3D printing integrated tunnel lining structure and construction method thereof

Abstract

The application relates to the technical field of tunnel engineering, and particularly discloses a 3D printing integrated tunnel lining structure and a construction method thereof. The structure is sequentially provided with a concrete leveling layer, a spray membrane waterproof layer and a concrete functional layer from the side of surrounding rock inward, and is particularly suitable for supporting and waterproof construction of underground engineering such as highway tunnels, railway tunnels, urban rail transit tunnels and the like. Based on the integrated design concept, the structure is adaptively designed according to the surrounding rock grade, the spray membrane waterproof layer and the concrete functional layer are cooperatively formed by using the 3D printing technology, the bearing capacity of the lining structure is significantly improved while meeting the waterproof requirement, the construction period is effectively shortened, and the construction cost is reduced. The performance and construction efficiency of the tunnel lining structure are improved.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, specifically to a 3D-printed integrated tunnel lining structure and its construction method. Background Technology

[0002] In tunnel construction, the lining structure, as the permanent support system of the tunnel, not only needs to withstand the pressure of the surrounding rock but also needs to have reliable waterproof performance to prevent groundwater from seeping into the tunnel and affecting its operational safety and service life. Traditional tunnel lining construction usually adopts a step-by-step construction method of 'cast concrete + waterproof membrane laying'. First, a mortar leveling layer is constructed, then a waterproof membrane is laid on the leveling layer, and finally the main lining structure is formed by casting with formwork to achieve structural support and waterproofing functions. However, traditional construction methods have many drawbacks: First, the step-by-step construction process is cumbersome, requiring separate leveling layer, waterproofing membrane laying, and lining main body pouring, resulting in a long construction cycle. Furthermore, the connection between each process is easily affected by human error, leading to weak bonding between structural layers and poor overall performance. Second, the waterproofing membrane is prone to wrinkles and damage during laying, and the bonding strength between the waterproofing membrane and the leveling layer and lining main body is insufficient, easily forming water channels and resulting in low waterproofing reliability. Third, traditional cast-in-place concrete construction relies heavily on formwork, leading to significant material waste. In complex geological conditions (such as curved tunnels and large-section tunnels), formwork processing and installation are difficult, making it hard to guarantee construction accuracy. Fourth, it does not provide differentiated design for different surrounding rock grades. For lower-strength Class III, IV, and V surrounding rock, a single lining structure is insufficient to meet support requirements, easily leading to risks such as lining cracking and surrounding rock deformation. With the development of 3D printing technology in the field of civil engineering, its advantages such as "digital modeling, automated molding, and on-demand material placement" provide a new solution for tunnel lining construction. Some studies have attempted to apply 3D printing technology to the construction of tunnel lining structures. However, existing technologies mostly focus only on the printing and shaping of the lining structure, without considering differentiated design based on the surrounding rock grade (e.g., support components required for low-strength surrounding rock are not integrated into the process). Furthermore, they lack systematic optimization of the integrated design and printing process for the leveling layer, sprayed waterproof layer, and main structure. This results in difficulties in synergistically achieving waterproofing, structural load-bearing capacity, and surrounding rock support requirements, leading to problems such as insufficient waterproofing reliability, low construction efficiency, and poor geological adaptability. Therefore, developing a structure that can be differentiated based on the surrounding rock grade and achieve integrated 3D printing of the leveling layer, sprayed waterproof layer, concrete functional layer, and support components is crucial for solving the current challenges in tunnel lining construction. Summary of the Invention

[0003] (a) Technical problems to be solved One objective of this invention is to overcome the shortcomings of existing tunnel lining construction, such as "step-by-step construction, low waterproof reliability, poor structural integrity, and weak geological adaptability," and to provide a construction method for a 3D-printed integrated tunnel lining structure with a short construction cycle and low construction cost.

[0004] Another objective of this invention is to achieve the coordinated molding of the outermost leveling layer, the sprayed waterproof layer, the concrete functional layer and the support components by combining integrated 3D printing technology with the surrounding rock grade adaptation design (such as adding 2.5D steel mesh to low-strength surrounding rock), thereby improving the overall load-bearing capacity, waterproof performance and geological adaptability of the lining structure.

[0005] (II) Technical Solution To achieve the above objectives, the present invention provides a construction method for a 3D-printed integrated tunnel lining structure, which includes, from the inner side to the outer side of the tunnel surrounding rock: a concrete functional layer, a sprayed waterproof layer, and an outermost leveling layer; the concrete functional layer, the sprayed waterproof layer, and the outermost leveling layer are formed into a tightly bonded integral structure through a 3D printing integrated molding process; and are differentiated according to the tunnel surrounding rock grade (Grade I-V).

[0006] If the surrounding rock is Class I, no additional support components are required. Only a basic structure of "leveling layer + sprayed waterproof layer + concrete functional layer" is used. The outermost leveling layer is printed using 3D printing equipment, and the printing thickness is adjusted in real time to ensure surface flatness. After the surface temperature of the outermost leveling layer drops below 50℃, the sprayed waterproof layer is applied, and then the concrete functional layer is sprayed using 3D printing equipment. If the surrounding rock is of grade II or IIIa, at least one or more layers of 2D steel mesh are embedded during the printing of the concrete functional layer. The mesh is made of HRB400 grade steel bars with a diameter of 8mm to 20mm and a mesh spacing of 100 to 200mm. The preferred mesh size is 150mm × 150mm. The 2D steel mesh is embedded synchronously during the printing of the concrete functional layer through the auxiliary installation module of the 3D printing robot. If the surrounding rock is classified as IIIb-c, IV, or V, after the waterproof membrane is sprayed, a steel arch frame is erected, and then the concrete functional layer is printed. During the printing of the concrete functional layer, a 2.5D steel mesh is embedded. The 2.5D steel mesh uses HRB400 grade steel bars with a diameter of 8mm~28mm, preferably 16~25mm, and a mesh spacing of 150mm×150mm. It is implanted simultaneously during the printing of the concrete functional layer using the auxiliary installation module of a 3D printing robot.

[0007] Furthermore, the 3D printing equipment has multiple types of printing nozzles and multiple storage bins, including at least a first storage bin for storing sprayed concrete material for the leveling layer, a second storage bin for storing acrylate sprayed waterproof material for the waterproof layer, a third storage bin for storing 3D printed water-repellent concrete material for the water-repellent layer in the functional concrete layer, and a third storage bin for storing 3D printed impermeable concrete material for the impermeable layer in the functional concrete layer. Each storage bin is connected to a printing nozzle, and a solenoid valve is installed on its connecting pipeline. The 3D printing equipment also includes a control unit and an auxiliary installation module. The auxiliary installation module is used to automatically install steel mesh and steel arch frame through a robotic arm. The control unit is used to communicate with each solenoid valve, auxiliary installation module, and printing nozzle to control the operation of the corresponding printing nozzle, complete the spraying of different materials, and lay the steel arch frame and steel mesh.

[0008] Furthermore, the outermost leveling layer uses ordinary shotcrete material with a strength grade of C20; the sprayed waterproof layer uses acrylate sprayed waterproof material with a curing time of <5s, a tensile strength at break of >1.1MPa, an elongation at break of >200%, a tear strength of 0.2kN / m, and after curing, its interlayer bond strength with the outermost leveling layer is not less than 2.0MPa, and its interlayer bond strength with the concrete functional layer is not less than 1.8MPa. The concrete functional layer includes a hydrophobic layer and an impermeable layer. The hydrophobic layer is set in close contact with the sprayed waterproof layer. The hydrophobic layer is made of 3D printed hydrophobic concrete material with a hydrophobic angle of 90°~120°, a water absorption rate of <3% in 48h, and a water resistance of 80%. The impermeable layer is made of 3D printed impermeable concrete material with a compressive strength >40MPa, a flexural strength >4MPa, and an impermeability >P13.

[0009] Furthermore, the thickness of the outermost leveling layer is adjusted according to the excavation conditions; the thickness of the sprayed waterproof layer is 2-2.5mm; the thickness of the concrete functional layer is determined according to the surrounding rock grade and design requirements, ranging from 300mm to 800mm.

[0010] The present invention also protects a 3D printed integrated tunnel lining structure, which includes, from the side of the tunnel surrounding rock inward, the following layers in sequence: an outermost leveling layer (3), a sprayed waterproof layer (2), and a concrete functional layer (1). At least one layer of 2.5D steel mesh is embedded in the concrete functional layer. The 2.5D steel mesh is composed of a planar steel mesh and hooks vertically connected to the nodes of the planar steel mesh, so that the 2.5D steel mesh has three-dimensional spatial connection characteristics on the basis of two-dimensional planar reinforcement.

[0011] (III) Beneficial Effects Compared with the prior art, the beneficial effects of the present invention are: This invention achieves continuous construction of the foundation layer structure through a 3D printing integrated molding process, while incorporating differentiated settings based on the surrounding rock grade (adding 2.5D steel mesh and steel arches for low-strength surrounding rock). Compared to leveling the surrounding rock first and then laying the waterproof layer template, this invention lays the waterproof layer using a spraying process before constructing the secondary lining. This gives the lining structure both overall load-bearing and waterproofing capabilities, and allows it to adapt to the support requirements under different geological conditions. This effectively avoids lining cracking and surrounding rock deformation problems in tunnels with low-strength surrounding rock. This integrated molding + surrounding rock adaptation construction method significantly improves structural safety.

[0012] This invention improves the traditional single secondary lining into a multi-material, 3D-printable composite concrete functional layer. It replaces the traditional requirement of pre-laying EVA waterproofing boards with sprayed waterproofing materials. This dual waterproofing system, combined with differentiated material adjustments (such as introducing self-healing materials into the Class V surrounding rock concrete functional layer), forms a hydrophobic layer and an impermeable layer with the composite concrete functional layer. It can cope with groundwater environments of different surrounding rock grades, and its waterproofing reliability is far higher than that of the traditional single waterproofing board structure.

[0013] This invention boasts high construction efficiency and low cost: the integrated 3D printing process eliminates the need for traditional templates and waterproofing membranes, and the differentiated design avoids material waste caused by excessive support; simultaneously, the support components (2.5D steel mesh) and the shotcrete functional layer are constructed concurrently, requiring no additional procedures, shortening the construction cycle and reducing costs compared to traditional methods. It also offers strong adaptability: through digital modeling and 3D printing parameter adjustment, repetitive geological surveys and trial-and-error during construction are avoided, allowing for flexible adaptation to tunnel projects with different surrounding rock grades and cross-sectional forms, balancing safety and economy. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention.

[0015] Figure 2 This is a detailed rendering of the structure of the present invention.

[0016] Figure 3 A schematic diagram of the construction process for 3D-printed integrated tunnel lining structures.

[0017] Among them, 1-concrete functional layer, 2-sprayed waterproof layer, 3-concrete leveling layer. Detailed Implementation

[0018] To further illustrate the technical solution of the present invention, the following detailed description is provided in conjunction with specific embodiments of different surrounding rock grades.

[0019] The present invention provides a 3D printed integrated tunnel lining structure, which is applicable to various tunnel cross-sections such as circular, horseshoe, and rectangular, especially irregular ones. From the outside of the tunnel surrounding rock (the side closest to the surrounding rock is the outside, and the side away from the surrounding rock is the inside) to the inside, it includes the following layers in sequence: the outermost leveling layer (3), the sprayed waterproof layer (2), and the concrete functional layer (1).

[0020] The outermost leveling layer is made of ordinary shotcrete material with a strength grade of C20.

[0021] The sprayed waterproof layer is an acrylate sprayed waterproof material composed of liquid A and liquid B. The curing time is <5s, the tensile strength at break is greater than 1.1MPa, the elongation at break is >200%, the tear strength is 0.2kN / m, and after curing, the interlayer bond strength between it and the outermost leveling layer is not less than 2.0MPa, and the interlayer bond strength between it and the concrete functional layer is not less than 1.8MPa.

[0022] The concrete functional layer includes a hydrophobic layer and an impermeable layer. The hydrophobic layer is adjacent to the sprayed waterproof layer and is made of 3D printed hydrophobic concrete material (hydrophobic angle 90°~120°, water absorption rate <3% (48h), water resistance 80%) and 3D printed impermeable concrete material (compressive strength >40MPa, flexural strength >4MPa, impermeability >P13).

[0023] The thickness of the outermost leveling layer is adjusted according to the excavation conditions; the thickness of the sprayed waterproof layer is usually 2mm; the thickness of the concrete functional layer depends on the surrounding rock grade and design requirements, and is usually 300mm-800mm. 3D-printed integrated tunnel lining structures, combined with differentiated designs based on surrounding rock grade, can be further subdivided into the following types: Class I surrounding rock (high strength, good stability) No additional support components are required; the foundation structure consists of a leveling layer, a waterproof spray layer, and a functional concrete layer.

[0024] Class II and IIIa surrounding rock (medium strength, self-stabilizing surrounding rock) A 2D steel mesh is added inside the concrete functional layer. The mesh uses HRB400 grade steel bars with a diameter of 8mm~20mm and a grid spacing of 150mm×150mm. The steel mesh is simultaneously implanted into the concrete functional layer during printing using the auxiliary installation module of a 3D printing robot.

[0025] Class IIIb-c, IV, and V surrounding rock (low strength, poor stability) A steel arch frame and a 2.5D steel mesh are added inside the concrete functional layer. The steel arch frame is erected after the waterproofing membrane is applied. The 2.5D steel mesh (prefabricated in the factory, with steel reinforcement arrangement) uses HRB400 grade steel bars with a diameter of 16mm~28mm and a grid spacing of 150mm×150mm. It is simultaneously implanted during the printing of the concrete functional layer using the auxiliary installation module of a 3D printing robot.

[0026] The 2.5D steel mesh consists of planar steel mesh grids and hooks vertically connected to its nodes, giving the steel mesh three-dimensional spatial connectivity on the basis of two-dimensional planar reinforcement.

[0027] The construction method for 3D-printed integrated tunnel lining structures includes the following steps: (S1) Laser scanning acquires a three-dimensional model of the tunnel surrounding rock surface. (S2) Generate 3D printed integrated lining structure design drawings and digital models; (S3) Use 3D printing equipment to print the outermost leveling layer, and adjust the printing thickness in real time to ensure surface flatness; (S4) Wait until the surface temperature of the outermost leveling layer drops below 50°C before applying the waterproof coating. (S5) If it is necessary to lay steel arches or steel mesh, then erect steel arches after the waterproof layer, and then print the concrete functional layer. At least one or more layers of steel mesh are embedded during the printing of the concrete functional layer. (S6) Quality inspection will be carried out after 7 days of curing.

[0028] According to the present invention, the outermost leveling layer is in direct contact with the surrounding rock of the tunnel and is used to fill the unevenness of the surrounding rock surface, providing a flat and uniform base surface for the construction of the sprayed waterproof layer; the outermost leveling layer adopts a 3D printing special leveling mortar material, the main components of which include: Portland cement, quartz sand, ultrafine fly ash, polypropylene fiber, redispersible latex powder and water; the thickness of the outermost leveling layer is determined according to the flatness of the surrounding rock surface and the uniform distribution of the thickness is achieved by digital control of the 3D printing nozzle.

[0029] According to the present invention, the sprayed waterproof layer is located between the outermost leveling layer and the concrete functional layer, serving as the main waterproof barrier of the lining structure to prevent groundwater from seeping into the tunnel from the surrounding rock. The sprayed waterproof layer uses a 3D-printed spray-type waterproof material, the main components of which are: epoxy resin, curing agent, nano-silica, graphene-modified filler, and defoamer. The sprayed waterproof layer is formed by atomization spraying through a 3D printing nozzle. The spraying process is continuous with the printing process of the outermost leveling layer. The sprayed waterproof layer is constructed immediately after the outermost leveling layer is printed and its surface temperature drops below 50°C. The thickness of the sprayed waterproof layer is 2mm-5mm, the tensile strength at break is greater than 1.1MPa, the elongation at break is greater than 200%, the tear strength is 0.2kN / m, and after curing, its interlayer bond strength with the outermost leveling layer is not less than 2.0MPa, and its interlayer bond strength with the concrete functional layer is not less than 1.8MPa.

[0030] According to the present invention, the concrete functional layer is located inside the sprayed waterproof layer, serving as a secondary waterproof barrier for the lining structure, while also possessing a certain structural load-bearing function, and working in conjunction with the sprayed waterproof layer to achieve a dual waterproofing effect; the concrete functional layer uses a 3D-printed special self-waterproof concrete material, the main components of which include: low heat of hydration cement, recycled aggregate, expansion agent, polyacrylonitrile fiber, waterproofing agent and water. The concrete functional layer includes a hydrophobic layer and an impermeable layer, which are respectively made of 3D printed hydrophobic concrete material (hydrophobic angle 90°~120°, water absorption rate <3% (48h), water resistance 80%) and 3D printed impermeable concrete material (compressive strength >40MPa, flexural strength >4MPa, impermeability >P13).

[0031] According to this invention, for Class I surrounding rock, no additional support components are required; only a foundation structure of "leveling layer + sprayed waterproof layer + concrete functional layer" is used. For Class II and IIIa surrounding rock (medium strength, self-stabilizing surrounding rock), a 2D steel mesh is added within the concrete functional layer. The mesh uses HRB400 grade steel bars with a diameter of 8mm~20mm and a grid spacing of 150mm×150mm. The 2D steel mesh is simultaneously implanted during the printing of the concrete functional layer using an auxiliary installation module of a 3D printing robot. For Class IIIb-c, IV, and V surrounding rock (low strength, poor stability), a double-layer 2.5D steel mesh is added: a steel arch frame and a 2.5D steel mesh are added within the concrete functional layer. The steel arch frame is erected after the sprayed waterproof layer is completed. The 2.5D steel mesh uses HRB400 grade steel bars with a diameter of 16mm~28mm and a grid spacing of 150mm×150mm, and is simultaneously implanted during the printing of the concrete functional layer using an auxiliary installation module of a 3D printing robot.

[0032] According to the present invention, digital modeling is first performed; then, 3D printing of the outermost leveling layer, the sprayed waterproof layer, and the concrete functional layer are performed in sequence; finally, curing and testing are carried out.

[0033] 3D printing integration means: 1. Construction process: The concrete functional layer, the sprayed waterproof layer, and the outermost leveling layer can all be completed using the same 3D printing equipment; 2. Lining structure: The waterproofing process, such as pre-laying EVA waterproofing boards, is replaced with a sprayed waterproofing layer, which improves the adhesion between the concrete functional layer and the outermost leveling layer, thereby enhancing the overall integration of the lining. 3. Materials: The concrete functional layer is transformed into a multi-material composite lining (water-repellent layer and impermeable layer), forming an integrated material structure.

[0034] Example 1 Reference Figure 1 and Figure 2 The same 3D printing equipment can be used to complete the concrete functional layer, the sprayed waterproof layer, and the outermost leveling layer. Furthermore, the Class IIIa surrounding rock is self-stabilizing, requiring only a safety reserve construction method—embedding 2D steel mesh within the concrete functional layer. Overview of a highway tunnel construction project in Class IIIa surrounding rock: This highway tunnel is a two-way four-lane tunnel with a circular cross-section and an excavation diameter of 12m. The surrounding rock is Class IIIa, with localized joints and fissures, and its stability is generally moderate. There is no large-scale groundwater.

[0035] Parameters of each structural layer

[0036] Key construction steps (1) When digitally modeling, mark the steel mesh implantation path in the concrete functional layer to ensure that the coverage of the steel mesh is completely matched with the concrete functional layer; (2) When the concrete functional layer is printed to a thickness of 6mm (total design thickness 120mm), the 2D steel mesh is laid flat on the surface by the auxiliary robotic arm of the 3D printing robot to ensure the position of the steel mesh; (3) Continue printing the remaining thickness of the concrete functional layer. During the printing process, start the vibration device at the end of the nozzle to avoid voids under the steel mesh. (4) After the concrete functional layer is printed, it is cured by spraying water for 7 days. Spray water 3 times a day for the first 3 days to keep the surface moist (moisture content ≥90%).

[0037] The 3D printing equipment used in construction has multiple types of printing nozzles and multiple storage bins, including a first storage bin for storing sprayed concrete material for the leveling layer, a second storage bin for storing acrylate sprayed waterproofing material for the waterproof layer, a third storage bin for storing 3D-printed water-repellent concrete material for the water-repellent layer in the functional concrete layer, and a fourth storage bin for storing 3D-printed impermeable concrete material for the impermeable layer in the functional concrete layer. Each storage bin is connected to a printing nozzle, and a solenoid valve is installed on its connecting pipeline. The 3D printing equipment also includes a control unit and an auxiliary installation module. The auxiliary installation module is used to automatically install steel mesh and steel arches using a robotic arm. The control unit is used to communicate with each solenoid valve, auxiliary installation module, and printing nozzle to control the operation of the corresponding printing nozzles, complete the spraying of different materials, and lay the steel arches and steel mesh.

[0038] Example 2 Reference Figure 1 and Figure 2 The concrete functional layer, the sprayed waterproof layer, and the outermost leveling layer were all completed using the same 3D printing facility. The surrounding rock is Class V and is non-self-stabilizing, requiring a structurally load-bearing 2.5D steel mesh. This urban rail transit tunnel is a double-track tunnel with a rectangular cross-section, an excavation size of 10m × 6m, and Class V surrounding rock, consisting of soft rock strata with poor stability and localized water seepage, necessitating strong support and a high level of waterproofing.

[0039] The 2.5D steel mesh consists of a planar steel mesh and hooks vertically connected to the nodes of the planar steel mesh, giving the steel mesh a three-dimensional spatial connection characteristic on the basis of two-dimensional planar reinforcement.

[0040] The hooks are preferably double-hook structures, with mechanical snap-fit ​​structures at the ends for quick connection with another layer of steel mesh. The bifurcation angle of the double hooks is 30°~60°, and their height is adapted to the interlayer design distance of the two-dimensional planar steel mesh, ranging from 15-25mm. They are arranged on the two-dimensional planar steel mesh in an outer node + inner quincunx pattern.

[0041] Parameters of each structural layer

[0042] Key construction steps (1) Before construction, the surrounding rock is scanned by ground-penetrating radar to determine the anchor bolt insertion location (avoiding areas with developed fissures). An anchor bolt drilling rig is used to insert longitudinal anchor bolts. After insertion, cement grout (water-cement ratio 0.5) is injected by grouting pump to ensure that the anchor bolts are tightly bonded to the surrounding rock. (2) The anchor bolt insertion depth and exposed length are detected by laser. After passing the test, the outermost leveling layer is printed. During printing, the robot's laser range sensor avoids the anchor bolt position in real time. The printing thickness of the leveling layer is dynamically adjusted according to the unevenness of the surrounding rock surface. (3) After the outermost leveling layer is printed, clean the rust from the exposed end of the anchor rod (exposing the metallic luster), and weld the outer 2.5D steel mesh to the anchor rod by robot welding; (4) When constructing the sprayed waterproof layer, the spraying speed should be matched with the printing speed of the outermost leveling layer. The construction should be carried out in the order of arch top → arch foot → side wall to ensure that the waterproof material evenly covers the surface of the leveling layer and around the anchor holes, without any missed spraying or hollowing.

[0043] Example 3 This embodiment of the 3D-printed integrated tunnel lining structure includes, from the tunnel surrounding rock side inwards: an outermost leveling layer 3, a sprayed waterproof layer 2, and a concrete functional layer 1. At least one layer of 2.5D steel mesh is embedded in the concrete functional layer (the specific number of 2.5D steel mesh layers is determined according to the actual situation). The 2.5D steel mesh consists of planar steel mesh and hooks vertically connected to the nodes of the planar steel mesh, so that the 2.5D steel mesh has three-dimensional spatial connection characteristics on the basis of two-dimensional planar reinforcement.

[0044] The outermost leveling layer is made of ordinary shotcrete with a strength grade of C20.

[0045] The raw materials for 3D-printed impermeable concrete, by weight, are: 100 parts cement, 100-120 parts fine aggregate, 15-25 parts fly ash, 5-7 parts nano-SiO2, 2.0-2.5 parts glass fiber, 0.5-1.5 parts water-reducing agent (polycarboxylate series), and 0.10-0.15 parts water-retaining agent. This 3D-printed impermeable concrete material achieves impermeability, densification, prevention of moisture loss, and ensures interlayer bonding and meets the requirements of 3D inkjet printing.

[0046] 3D Printing Hydrophobic Concrete Material: 100 parts cement, 100-120 parts fine aggregate, 5-8 parts silica fume, 0.8 parts WR80 water-repellent agent, 0.8-1.2 parts water-reducing agent, 0.10-0.20 parts cellulose ether, and 26-28 parts water. This 3D printing hydrophobic concrete material meets the requirements of 3D inkjet printing, has enhanced crack resistance and water-repellent properties, and ensures interlayer adhesion.

[0047] The materials used in this embodiment are commonly used in the field and are readily available from commercially available sources.

[0048] This invention adds a sprayed waterproof layer, which, during construction, better integrates the outermost leveling layer with the concrete functional layer, improving overall integrity compared to traditional lining. The sprayed waterproof layer is laid out using 3D printing, eliminating the need to replace construction equipment (which is the same equipment used for the outermost leveling layer). This results in a 3D-printed integrated tunnel lining structure, with the entire construction cycle completed using 3D printing. It allows for more refined and differentiated adaptation designs to different surrounding rock grades; it eliminates the need for pre-laying EVA waterproofing sheets; and it uses the concrete functional layer as a secondary waterproof barrier within the lining structure, while also providing structural load-bearing capacity. Working in synergy with the sprayed waterproof layer, it achieves a dual waterproofing effect, making the waterproof layer more stable and less prone to damage, thus improving the overall performance, construction efficiency, and geological adaptability of the tunnel lining.

[0049] Example 4 In this embodiment, the sprayed waterproof layer is composed of an acrylate sprayed waterproof material made from a mixture of liquid A and liquid B, as well as expanding particles, which enhances the waterproof effect.

[0050] In summary, the 3D-printed integrated tunnel lining structure of this invention enables the coordinated molding of each functional layer of the lining structure and the support components, thereby improving the overall performance, construction efficiency, and geological adaptability of the tunnel lining.

[0051] The above description is only a preferred embodiment of the present invention. For those skilled in the art, there will be changes in the specific implementation and application scope based on the ideas of the present invention. The content of this specification should not be construed as a limitation of the present invention.

[0052] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A construction method for a 3D-printed integrated tunnel lining structure, characterized in that, From the side of the tunnel surrounding rock inward, it includes: the outermost leveling layer (3), the sprayed waterproof layer (2), and the concrete functional layer (1); If the surrounding rock is Class I, no additional support components are required. Only a basic structure of "leveling layer + sprayed waterproof layer + concrete functional layer" is used. The outermost leveling layer is printed using 3D printing equipment, and the printing thickness is adjusted in real time to ensure surface flatness. After the surface temperature of the outermost leveling layer drops below 50℃, the sprayed waterproof layer is applied, and then the concrete functional layer is sprayed using 3D printing equipment. If the surrounding rock is of grade II or IIIa, at least one or more layers of 2D steel mesh are embedded during the printing of the concrete functional layer. The mesh is made of HRB400 grade steel bars with a diameter of 8mm to 20mm and a mesh spacing of 150mm × 150mm. The 2D steel mesh is embedded synchronously during the printing of the concrete functional layer through the auxiliary installation module of the 3D printing robot. If the surrounding rock is classified as IIIb-c, IV, or V, after the waterproof membrane is applied, a steel arch frame is erected, and then the concrete functional layer is printed. During the printing of the concrete functional layer, a 2.5D steel mesh is embedded. The 2.5D steel mesh uses HRB400 grade steel bars with a diameter of 8mm~28mm and a mesh spacing of 100~200mm. It is embedded synchronously during the printing of the concrete functional layer using the auxiliary installation module of the 3D printing robot.

2. The construction method according to claim 1, characterized in that, The 3D printing equipment has multiple types of printing nozzles and multiple storage bins, including at least a first storage bin for storing sprayed concrete material for the leveling layer, a second storage bin for storing acrylate sprayed waterproof material for the waterproof layer, a third storage bin for storing 3D printed water-repellent concrete material for the water-repellent layer in the functional concrete layer, and a third storage bin for storing 3D printed impermeable concrete material for the impermeable layer in the functional concrete layer. Each storage bin is connected to a printing nozzle, and a solenoid valve is installed on its connecting pipeline. The 3D printing equipment also includes a control unit and an auxiliary installation module. The auxiliary installation module is used to automatically install steel mesh and steel arch frame through a robotic arm. The control unit is used to communicate with each solenoid valve, auxiliary installation module, and printing nozzle to control the operation of the corresponding printing nozzle to complete the spraying of different materials and the laying of steel arch frame and steel mesh.

3. The construction method according to claim 1, characterized in that, The outermost leveling layer uses ordinary shotcrete material with a strength grade of C20; the sprayed waterproof layer uses acrylate sprayed waterproof material with a curing time of <5s, a tensile strength at break of >1.1MPa, an elongation at break of >200%, a tear strength of 0.2kN / m, and after curing, its interlayer bond strength with the outermost leveling layer is not less than 2.0MPa, and its interlayer bond strength with the concrete functional layer is not less than 1.8MPa. The concrete functional layer includes a hydrophobic layer and an impermeable layer. The hydrophobic layer is set in close contact with the sprayed waterproof layer. The hydrophobic layer is made of 3D printed hydrophobic concrete material with a hydrophobic angle of 90°~120°, a water absorption rate of <3% in 48h, and a water resistance of 80%. The impermeable layer is made of 3D printed impermeable concrete material with a compressive strength >40MPa, a flexural strength >4MPa, and an impermeability >P13.

4. The construction method according to claim 1, characterized in that, The thickness of the outermost leveling layer is adjusted according to the excavation conditions; the thickness of the sprayed waterproof layer is 2-2.5mm; the thickness of the concrete functional layer is determined according to the surrounding rock grade and design requirements, and is 300mm-800mm.

5. A 3D-printed integrated tunnel lining structure, characterized in that, From the side of the tunnel surrounding rock inward, it includes: the outermost leveling layer (3), the sprayed waterproof layer (2) and the concrete functional layer (1). At least one layer of 2.5D steel mesh is embedded in the concrete functional layer. The 2.5D steel mesh is composed of planar steel mesh and hooks vertically connected to the nodes of the planar steel mesh, so that the 2.5D steel mesh has three-dimensional spatial connection characteristics on the basis of two-dimensional planar reinforcement.

6. The 3D-printed integrated tunnel lining structure according to claim 5, characterized in that, The outermost leveling layer uses ordinary shotcrete material with a strength grade of C20; the sprayed waterproof layer uses acrylate sprayed waterproof material with a curing time of <5s, a tensile strength at break of >1.1MPa, an elongation at break of >200%, a tear strength of 0.2kN / m, and after curing, its interlayer bond strength with the outermost leveling layer is not less than 2.0MPa, and its interlayer bond strength with the concrete functional layer is not less than 1.8MPa. The concrete functional layer includes a hydrophobic layer and an impermeable layer. The hydrophobic layer is set in close contact with the sprayed waterproof layer. The hydrophobic layer is made of 3D printed hydrophobic concrete material with a hydrophobic angle of 90°~120°, a water absorption rate of <3% in 48h, and a water resistance of 80%. The impermeable layer is made of 3D printed impermeable concrete material with a compressive strength >40MPa, a flexural strength >4MPa, and an impermeability >P13.

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