Method and system for manufacturing roadway surrounding rock stratified bearing structure and testing performance of roadway surrounding rock stratified bearing structure

Abstract

The invention belongs to the technical field of performance testing of roadway surrounding rock structures, and discloses a manufacturing and performance testing method and system for a roadway surrounding rock stratified bearing structure. According to the method, three-dimensional coordinates are constructed for a roadway surrounding rock stratified bearing structure model manufactured through the roadway surrounding rock stratified bearing structure manufacturing method based on 3D printing, 3D printing is conducted, and the roadway surrounding rock stratified bearing structure model is formed; carrying out mechanical property testing on the formed roadway surrounding rock stratified bearing structure model by utilizing a roadway surrounding rock stratified bearing structure performance testing method based on 3D printing; and finally obtaining the optimized roadway surrounding rock stratified bearing structure based on a mechanical property test result. The method solves the problem that the influence of a layered structure and parameters thereof on the bearing performance of the surrounding rock is not considered in the indoor manufacturing of the existing roadway surrounding rock structure.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel surrounding rock structure performance testing, and in particular relates to a tunnel surrounding rock layered bearing structure manufacturing and performance testing method and system. Background Art

[0002] After the coal mine tunnel is excavated, the tunnel surrounding rock can be divided into fracture layer, plastic softening layer, elastic layer and original rock stress layer (zone) from outside to inside according to the degree of deformation and damage. The superimposed layered structure jointly bears the pressure acting on the tunnel. Therefore, when designing the support of coal mine tunnels, the calculation of support parameters based on the principle of bearing layering has become one of the widely used and effective support design methods in coal mines. It can be seen that mastering the relationship between the layered characteristics and parameters of the tunnel surrounding rock and the bearing capacity of the tunnel surrounding rock is of great significance to the tunnel support design.

[0003] At present, the layered rock structure and parameters of the tunnel are generally obtained through field detection or numerical simulation. The layered structure parameters obtained by field detection are only for the tunnels in the selected specific section, and the surrounding rock structure parameters of tunnels in different sections often vary. Therefore, the field detection method cannot meet the requirements of adjusting the tunnel support parameters due to the change of layered structure parameters. Although the numerical simulation method can solve this problem, the construction of the theory and numerical model in the numerical simulation software has been simplified to a certain extent, and the simulation results are difficult to truly reflect the characteristics of the layered structure of the tunnel.

[0004] Indoor test is an effective method to study on-site problems, but due to the lack of the principle of making layered surrounding rock structure and the unreality of actual operation, the method of studying the bearing performance of layered surrounding rock structure of tunnel through indoor test has not been realized. With the development of 3D printing technology and its introduction in the field of rock mechanics, indoor imitation of tunnel surrounding rock has become a reality. For example, the invention patent with application publication number CN 113899767 A - Forming experimental method of tunnel surrounding rock experimental model based on 3D printing technology, announced a method for realizing the overall generation of tunnel surrounding rock with fractures through 3D printing technology, but this production method does not consider the layered bearing structure characteristics of tunnel surrounding rock, and it is even more impossible to study the influence of support and layered structure parameters on the bearing performance of surrounding rock, such as the thickness of each bearing layer, degree of damage, support parameters, etc. Based on this, a 3D printing method for making layered bearing structure of tunnel surrounding rock is proposed, which is used to quantitatively evaluate the influence of surrounding rock structure and support parameters on the mechanical properties of bearing structure, which is of great significance for tunnel support design and surrounding rock stability evaluation.

[0005] Through the above analysis, the problems and defects of the existing technology are: the indoor production of the existing tunnel surrounding rock structure does not take into account the influence of the layered structure and its parameters on the bearing capacity of the surrounding rock, the test accuracy is low, and the tunnel surrounding rock structure produced by the existing technology has poor bearing capacity of the surrounding rock. Summary of the invention

[0006] In order to overcome the problems existing in the related art, the embodiments disclosed in the present invention provide a method and system for manufacturing and performance testing of a layered bearing structure of tunnel surrounding rock, and specifically relate to a method for manufacturing and performance testing of a layered bearing structure of tunnel surrounding rock based on 3D printing.

[0007] The technical solution is as follows: a method for manufacturing a tunnel surrounding rock layered bearing structure and testing its performance, the method comprising the following steps:

[0008] S1, a method for making a layered bearing structure of tunnel surrounding rock based on 3D printing, making a model of the layered bearing structure of tunnel surrounding rock, constructing three-dimensional coordinates and performing 3D printing, and forming the model of the layered bearing structure of tunnel surrounding rock; designing a cross hollow body to represent the fracture damage, and distinguishing each layer by the volume proportion of the hollow body;

[0009] S2, the mechanical properties of the formed tunnel surrounding rock layered bearing structure model are tested using the tunnel surrounding rock layered bearing structure performance testing method based on 3D printing;

[0010] S3, based on the mechanical properties test results, the optimized layered bearing structure of the tunnel surrounding rock is obtained.

[0011] In step S1, three-dimensional coordinates are constructed and 3D printing is performed, including:

[0012] S101, classify the tunnel type and surrounding rock layer structure; determine the type of the model tunnel to be a semicircular arch tunnel, and take the inner wall of the tunnel as the starting point to divide the tunnel surrounding rock into a fracture layer, a plastic softening layer, an elastic layer and an original rock layer;

[0013] S102, determine the basic parameters of the tunnel surrounding rock layer bearing structure, the fracture layer parameters are: thickness h1, vertical wall height h b , radius of semicircular arch r1, damage degree D1;

[0014] The parameters of the plastic softening layer are: thickness h2, damage degree D2;

[0015] The elastic layer parameters are: thickness h3;

[0016] The original rock layer parameters are: thickness is h4;

[0017] S103, testing the mechanical properties of the tunnel surrounding rock mass;

[0018] S104, construction of a three-dimensional coordinate system;

[0019] S105, representation of damage to the fractured layer and the plastic softening layer; using a computer to construct a three-dimensional coordinate system, a three-dimensional coordinate system is established according to the actual size of the tunnel surrounding rock layered bearing structure model, and the three-dimensional construction of the overall outline of the tunnel surrounding rock layered bearing structure model is completed; multiple cross hollow bodies are used to represent the cracks in the layered structure, and the damage calculation formula of the fractured layer and the plastic softening layer is:

[0020]

[0021] Where D f is the sum of the volumes of the cross hollow bodies, D m is the overall volume of each structural layer;

[0022] S106, production of rupture layer;

[0023] S107, plastic softening layer production;

[0024] S108, elastic layer preparation;

[0025] S109, made from original rock layers;

[0026] S110, preparation of the layered bearing structure model of the surrounding rock of the overall tunnel.

[0027] In step S103, the mechanical properties of the tunnel surrounding rock mass are tested, including: taking samples of the surrounding rock mass to be studied in each layer for uniaxial compression test, and determining the damage variable ranges of the elastic stage and the plastic softening stage according to the stress-strain and damage calculation formula: 0-D1 is the damage variable range of the elastic zone, D1-D2 is the damage variable range of the plastic softening zone, and D1-1 is the damage variable range of the rupture zone;

[0028] The damage variable calculation formula is:

[0029]

[0030] Where E is the real-time elastic modulus of rock, and E0 is the initial elastic modulus of rock.

[0031] In step S106, the preparation of the rupture layer includes:

[0032] S1061, assuming that the damage of the rupture layer is D1, the volume of the cross hollow body is v1, and the number of cross damaged bodies is n1, then the damage of the rupture layer is:

[0033]

[0034] S1062, design cross hollow bodies evenly distributed in the layered structure;

[0035] S1063, determining the printing materials of the fracture layer rock, the printing materials include: river sand, ordinary P.O425 cement, water, water glass and water reducing agent, and the ratio of printing materials for different lithology rock masses needs to be determined in combination with the physical and mechanical properties of the actual rock masses;

[0036] S1064, three-dimensional spatial marking of the rupture layer boundary and cross damage volume;

[0037] S1065, cross-lesion body print.

[0038] In step S107, the plastic softening layer production includes:

[0039] S1071, assuming that the damage of the plastic softening layer is D2, the volume of the cross hollow body is v2, and the number of cross damaged bodies is n2, then the damage of the plastic softening layer is:

[0040]

[0041] S1072, the cross hollow body distribution design is similar to the rupture layer, and the number is reduced relative to the rupture layer;

[0042] S1073, determining the printing material of the plastic softening layer rock;

[0043] S1074, three-dimensional spatial marking of the plastic softening layer boundary and cross damage.

[0044] In step S108, the elastic layer manufacturing includes:

[0045] S1081, determining the printing material of the elastic layer rock;

[0046] S1082, determining the elastic layer boundary according to the structural parameters in S102, and performing three-dimensional space marking;

[0047] In step S109, the original rock layer production includes:

[0048] S1091, determine the printing material of the original rock layer;

[0049] S1092, the arc-shaped lower boundary of the original rock layer coincides with the arc-shaped upper boundary of the elastic layer, and the outer boundary of the vertical wall of the original rock layer coincides with the inner boundary of the vertical wall of the elastic layer;

[0050] In step S110, the overall model making includes: printing and molding through a sand mold 3D printer according to the constructed three-dimensional coordinates of the tunnel surrounding rock layered bearing structure model; using it for mechanical property testing after room temperature curing; printing parameters include the Z-AXIS value of the distance between the nozzle and the printing platform, the printing layer thickness, the printing speed and the printer filling rate; firstly, the printing Z-AXIS value is determined according to the comprehensive test of the specimen molding speed and molding accuracy under different Z-AXIS values, and then the printing layer thickness of 1.0mm~3.0mm and the printing speed of 150mm~300mm are determined according to the printer performance and the coarseness of the material; the filling method of the print selects the printer default filling rate.

[0051] In step S2, the mechanical properties test using the tunnel surrounding rock layered bearing structure performance test method based on 3D printing includes:

[0052] S201, placing the model on a biaxial loading test bench without any support, and applying hydrostatic pressure to a predetermined value;

[0053] S202, applying axial stress at a loading rate until the layered bearing structure of the tunnel surrounding rock is destroyed, and monitoring the stress-strain changes during the loading process;

[0054] S203, changing the layer thickness or damage degree, loading rate conditions, and repeating the above experimental steps;

[0055] S204, according to the monitored stress and deformation of each load-bearing layer and the sample as a whole, the stress and strain of the maximum load-bearing of the structure as a whole are obtained, and the load-bearing performance of the layered load-bearing structure is obtained;

[0056] S205, according to the maximum bearing strength and ultimate deformation of the layered bearing structure of the tunnel surrounding rock under different parameters of layer thickness, damage degree and loading rate, each parameter is used as the horizontal coordinate and the maximum bearing strength or ultimate deformation of the structure is used as the vertical coordinate to obtain the relationship between the bearing capacity of the structure and each layer thickness, damage degree and loading rate.

[0057] In step S201, strain gauges are respectively attached to the surfaces of the fracture layer, plastic softening layer, elastic layer, and original rock layer of the tunnel surrounding rock layered bearing structure model, and then connected to a static strain monitor for deformation monitoring;

[0058] In step S202, the loading rate is 0.06 mm / min.

[0059] Another object of the present invention is to provide a tunnel surrounding rock layered bearing structure, which is manufactured using the tunnel surrounding rock layered bearing structure manufacturing and performance testing method. The structure is composed of, from the inside to the outside: a fractured layer, a plastic softening layer, an elastic layer, and an original rock layer; the fractured layer, the plastic softening layer, and the elastic layer are all in the shape of a semicircular arch; and the original rock layer is a cube.

[0060] Furthermore, strain gauges are pasted at different positions of the fracture layer, plastic softening layer, elastic layer, and original rock layer, and then connected to a static strain monitor for deformation monitoring.

[0061] Combining all the above technical solutions, the beneficial effects of the present invention are as follows: by introducing a "cross" damage body to simulate the cracks in the rock strata, the degree of damage to the rock strata can be quantitatively characterized; with the help of 3D printing technology, the stratification phenomenon of actual tunnel surrounding rock damage can be simulated and restored in the laboratory, and by changing the thickness or damage degree of each layer, loading rate and other conditions, the compressive strength and ultimate deformation of the bearing structure, and its relationship with the parameters of the layered bearing structure can be tested, providing an effective indoor simulation method for obtaining the bearing capacity of the tunnel surrounding rock on site and optimizing the bearing parameters, solving the problem that the indoor production of the existing tunnel surrounding rock structure does not consider the influence of the layered structure and its parameters on the bearing performance of the surrounding rock.

[0062] The present invention reduces the difficulty of using original rock to make a layered structure of tunnel surrounding rock, saving manpower and time investment. The present invention proposes a method for making and testing the layered bearing structure of tunnel surrounding rock based on 3D printing, which provides an effective indoor simulation method for obtaining the bearing capacity of tunnel surrounding rock on site and optimizing bearing parameters, and solves the problem that the indoor production of existing tunnel surrounding rock structures does not consider the influence of layered structures and their parameters on the bearing performance of surrounding rocks. The present invention solves the problem that the degree of damage to tunnel surrounding rock cannot be quantitatively designed through the design of a cross hollow body, and the production of surrounding rock damage bodies is not limited to the use of cross hollow bodies. Other hollow structures such as "straight-shaped" and "fork-shaped" can refer to the method of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description, serve to explain the principles of the present disclosure;

[0064] Figure 1 It is a flow chart of a method for manufacturing and testing the performance of a tunnel surrounding rock layered bearing structure provided by an embodiment of the present invention;

[0065] Figure 2 It is a flow chart of a method for manufacturing a tunnel surrounding rock layered bearing structure based on 3D printing provided by an embodiment of the present invention;

[0066] Figure 3 It is a schematic diagram of the front structure of a tunnel surrounding rock layered bearing structure model for 3D printing provided by an embodiment of the present invention;

[0067] Figure 4 It is a stress-strain-damage diagram of layered division of a tunnel surrounding rock layered bearing structure model for 3D printing provided by an embodiment of the present invention;

[0068] Figure 5 It is a schematic diagram of the damage structure of the rupture layer and the plastic softening layer of the layered bearing structure model of the tunnel surrounding rock for 3D printing provided by an embodiment of the present invention;

[0069] Figure 6 It is a schematic diagram of the damage printing process of the fracture layer and the plastic softening layer of the layered bearing structure model of the tunnel surrounding rock for 3D printing provided by an embodiment of the present invention;

[0070] Figure 7 It is a full view of the damage structure of the fracture layer and the plastic softening layer of the layered bearing structure model of the tunnel surrounding rock for 3D printing provided by an embodiment of the present invention;

[0071] Figure 8 It is a schematic diagram of a method for manufacturing a tunnel surrounding rock layered bearing structure based on 3D printing provided by an embodiment of the invention;

[0072] Fig. 9 It is a flow chart of a method for testing the performance of a tunnel surrounding rock layered bearing structure based on 3D printing provided by an embodiment of the present invention;

[0073] Fig.10 It is a schematic diagram of the front structure of the tunnel surrounding rock layered bearing structure capable of testing the position of strain gauges based on 3D printing provided by an embodiment of the present invention;

[0074] In the figure: 1, fracture layer; 2, plastic softening layer; 3, elastic layer; 4, original rock layer; 5, static strain monitor; 501, strain gauge. DETAILED DESCRIPTION

[0075] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0076] The innovation of the present invention lies in: the present invention solves the problem that the degree of damage to the tunnel surrounding rock cannot be quantified by design through the design of a cross hollow body; a method for manufacturing a layered bearing structure of the tunnel surrounding rock based on 3D printing is proposed; combined with the above-mentioned layered bearing structure and performance testing method, an effective indoor simulation method is provided for obtaining the bearing capacity of the tunnel surrounding rock on site and optimizing the bearing parameters, which solves the problem that the indoor production of the existing tunnel surrounding rock structure does not consider the influence of the layered structure and its parameters on the bearing performance of the surrounding rock.

[0077] Embodiment 1, as shown in the figure, the method for manufacturing and testing the performance of the tunnel surrounding rock layered bearing structure provided by the embodiment of the present invention includes:

[0078] S1, a method for making a layered bearing structure of tunnel surrounding rock based on 3D printing, making a model of the layered bearing structure of tunnel surrounding rock, constructing three-dimensional coordinates and performing 3D printing, and forming the model of the layered bearing structure of tunnel surrounding rock; designing a cross hollow body to represent the fracture damage, and distinguishing each layer by the volume proportion of the hollow body;

[0079] S2, the mechanical properties of the formed tunnel surrounding rock layered bearing structure model are tested using the tunnel surrounding rock layered bearing structure performance testing method based on 3D printing;

[0080] S3, based on the mechanical properties test results, the optimized layered bearing structure of the tunnel surrounding rock is obtained.

[0081] Embodiment 2, as Figure 2 As shown, a method for manufacturing a tunnel surrounding rock layered bearing structure based on 3D printing provided by an embodiment of the present invention includes:

[0082] S101, classification of tunnel types and surrounding rock layer structures. Includes:

[0083] Determine the model laneway type as a semicircular arch laneway;

[0084] And, starting from the inner wall of the tunnel, the tunnel surrounding rock is divided into a fracture layer, a plastic softening layer, an elastic layer and an original rock layer;

[0085] S102, determine the basic parameters of the tunnel surrounding rock layered bearing structure. Including:

[0086] The parameters of the fracture layer are: thickness h1, vertical wall height h b , radius of semicircular arch r1, damage degree D1;

[0087] The parameters of the plastic softening layer are: thickness h2, damage degree D2;

[0088] The elastic layer parameters are: thickness h3;

[0089] The original rock layer parameters are: thickness is h4;

[0090] The tunnel surrounding rock bearing structure is a cube stacked structure composed of four layers of "arched" 3D printed rock layers. The four layers of "arched" 3D printed rock layers are the original rock layer, elastic layer, plastic softening layer and fracture layer. The damage of the "arched" 3D printed rock layer can be obtained by setting a cross hollow body. The performance test method of the layered bearing structure of the tunnel surrounding rock mainly refers to loading the cube stacked structure through a pressure testing machine, and the compressive strength and ultimate deformation of the bearing structure are obtained by testing. The bearing structure can obtain the relationship between the layered bearing structure parameters and its bearing performance by changing the layer thickness or damage degree, loading rate and other conditions, which provides an effective indoor simulation method for obtaining the bearing capacity of the tunnel surrounding rock and optimizing the bearing parameters.

[0091] The experimental model of the tunnel surrounding rock layered bearing structure is finally a cube with a side length of 30 cm. Figure 3 The layered bearing structure of the tunnel surrounding rock is as follows from the inside to the outside: fracture layer 1, plastic softening layer 2, elastic layer 3, original rock layer 4; the fracture layer 1, plastic softening layer 2, and elastic layer 3 are all in the shape of semicircular arches;

[0092] S103, test the mechanical properties of the tunnel surrounding rock mass.

[0093] Take samples of the surrounding rock mass to be studied in each layer for uniaxial compression test, and determine the damage variable range in the elastic stage and plastic softening stage according to the stress-strain and damage calculation formula, such as Figure 4 As shown, 0~D1 is the damage variable range of the elastic zone, D1~D2 is the damage variable range of the plastic softening zone, and D2~1 is the damage variable range of the fracture zone. Rock sample size: diameter 50mm, height 100mm.

[0094] The damage variable calculation formula is: D=1-E / E0, where E represents the real-time elastic modulus of rock and E0 represents the initial elastic modulus of rock.

[0095] S104, construction of a three-dimensional coordinate system.

[0096] A three-dimensional coordinate system is constructed using a computer, and a three-dimensional coordinate system is established according to the actual size of the model to complete the three-dimensional construction of the overall outline of the tunnel surrounding rock model.

[0097] S105, representation of damage in rupture layer and plastic softening layer.

[0098] The cross hollow body is designed to represent the simplified crack damage, such as Figure 5 As shown. Multiple cross hollow bodies are used to represent cracks in the layered structure. The damage calculation formula of the rupture layer / plastic softening layer is: Among them, D f represents the sum of the volumes of the cross hollow bodies, D m Represents the overall volume of each structural layer.

[0099] S106, making of a rupture layer, including:

[0100] S1061, assuming that the damage of the rupture layer is D1, the volume of the cross hollow body is v1, and the number of cross damaged bodies is n1, then the damage of the rupture layer is:

[0101]

[0102] The size and orientation of the cross hollow body structure can be adjusted through 16 coordinate points.

[0103] S1062, design cross hollow bodies evenly distributed in the layered structure;

[0104] S1063, determining the printing material of the fracture layer rock, including:

[0105] (1) The main materials are river sand (fineness modulus 1.0-2.0), ordinary P.O425 cement, water, water glass and water reducing agent. The printing material ratio of different rock masses needs to be determined in combination with the physical and mechanical properties of the actual rock mass, including rock mass density, particle size, uniaxial compressive strength, elastic modulus and tensile strength;

[0106] (2) After 28 days of solidification and curing, the physical and mechanical properties of the configured printing material and the actual physical and mechanical properties of the rock mass meet a certain similarity ratio.

[0107] S1064, three-dimensional space marking of the rupture layer boundary and cross damage volume. Including:

[0108] (i) Taking the center of the bottom edge as the coordinate center, determine the arc-shaped lower boundary of the fracture layer and the outer boundary line of the vertical wall according to the size of the specimen;

[0109] (ii) determining the arc upper boundary of the fracture layer and the vertical inner boundary range line of the fracture layer according to the structural parameters of the fracture layer in step S102;

[0110] (iii) Determine the specific value represented by n, and then calculate the distribution spacing of the cross hollow bodies. The spacing is based on the distance between the centers of the two cross hollow bodies. After determining the center position coordinates of each hollow body, determine the 16 coordinates of the cross hollow body around the center coordinates.

[0111] S1065, cross-lesion body print.

[0112] When the sand mold 3D printer is printing, the grouting is carried out in a straight line cycle. The grouting is stopped within the calibration range of the damaged body. After the grouting head moves beyond the calibration range, the normal grouting operation continues. The printing of a cross hollow body can refer to Figure 6As shown, before printing the first strip of the cross hollow body, the first strip is printed completely first, then the second strip is printed and stops at the hollow body position, and the third strip is printed across the reserved position of the hollow body, and the printing is continued in sequence until a complete printed strip 12 after the hollow body is completed.

[0113] S107, plastic softening layer production, including:

[0114] S1071, assuming that the damage of the plastic softening layer is D2, the volume of the cross hollow body is v2, and the number of cross damaged bodies is n2, then the damage of the plastic softening layer is:

[0115]

[0116] S1072, the cross hollow body distribution design is similar to the rupture layer, and the number is reduced relative to the rupture layer, such as Figure 7 As shown;

[0117] S1073, determining the printing material of the plastic softening layer rock, the specific method and materials are the same as S1063;

[0118] S1074, perform three-dimensional spatial marking on the boundary of the plastic softening layer and the cross damage, which is specifically the same as the operation of the fracture layer, wherein the arc-shaped lower boundary of the plastic softening layer coincides with the arc-shaped upper boundary line of the fracture layer, and the outer boundary of the vertical wall of the plastic softening layer coincides with the inner boundary of the vertical wall of the fracture layer, and the coordinates are consistent in the three-dimensional coordinate system.

[0119] S108, elastic layer production, including:

[0120] S1081, determining the printing material of the elastic layer rock, the specific method and materials are the same as S1063;

[0121] S1082, determine the boundary of the elastic layer according to the structural parameters in S102, and perform three-dimensional space marking, wherein the arc-shaped lower boundary of the elastic layer coincides with the arc-shaped upper boundary line of the plastic softening layer, and the outer boundary of the vertical wall of the elastic layer coincides with the inner boundary of the vertical wall of the plastic softening layer, and the coordinates are consistent in the three-dimensional coordinate system.

[0122] S109, original rock layer production, including:

[0123] S1091, determining the printing material of the original rock layer, the specific method and materials are the same as S1063;

[0124] S1092, the arc-shaped lower boundary of the original rock layer coincides with the arc-shaped upper boundary line of the elastic layer, and the outer boundary of the vertical wall of the original rock layer coincides with the inner boundary of the vertical wall of the elastic layer. Since the original rock layer has a large range in the real environment, in the research content applicable to this model, external pressure can be used to simulate the effect of the original rock layer on other layered structures, instead of constructing a large range of original rock layers. Therefore, in the model, only a certain thickness of the original rock layer is selected to show the relationship between the original rock layer and other layered structures, and the overall external contour boundary of the model is regarded as the boundary of the original rock layer.

[0125] The elastic layer material has a higher density than the original rock layer.

[0126] S110, overall model making.

[0127] According to the constructed three-dimensional coordinates of the model, the model is printed by a sand mold 3D printer and formed. After curing at room temperature (25±1.5C) for 28 days, it can be used for mechanical property testing.

[0128] Printing parameter settings: Printing parameters include the distance between the nozzle and the printing platform (Z-AXIS value), printing layer thickness, printing speed and printer filling rate. First, determine the printing Z-AXIS value based on the comprehensive test of the molding speed and molding accuracy of the test piece under different Z-AXIS values, and then determine the printing layer thickness (1.0mm~3.0mm) and printing speed (150mm~300mm) based on the printer performance and material coarseness; select the printer default filling rate for the printing filling method.

[0129] For example, Figure 8 This is the principle of the method for manufacturing a tunnel surrounding rock layered bearing structure based on 3D printing provided by an embodiment of the present invention.

[0130] Embodiment 3, as Fig. 9 As shown, the method for testing the performance of the tunnel surrounding rock layered bearing structure based on 3D printing provided by the embodiment of the present invention includes:

[0131] S201, without adding support, the model is placed on a biaxial loading test bench, and hydrostatic pressure (equal in axial and horizontal directions) is applied to a predetermined value at a speed of 0.05 MPa / s, and strain gauges 501 are respectively pasted on the surface of the multi-layer structure of the tunnel surrounding rock layered bearing structure model, and then connected to a static strain monitor 5 for deformation monitoring, such as Fig.10 shown.

[0132] S202, apply axial stress at a loading rate of 0.06 mm / min until the model is destroyed. Monitor the stress-strain changes during the loading process.

[0133] S203, changing the layer thickness or damage degree, loading rate and other conditions, and repeating the above experimental steps.

[0134] S204, based on the monitored stress and deformation of each bearing layer and the entire sample, the stress and strain of the maximum bearing capacity of the entire structure are obtained. At this time, the stress and strain of each bearing layer, that is, the bearing performance of the layered bearing structure, is obtained.

[0135] S205, according to the bearing performance of the structure under different parameters (layer thickness, damage degree and loading rate), each parameter is used as the horizontal coordinate and the maximum bearing stress of the structure is used as the vertical coordinate. The relationship between the bearing capacity of the structure and each layer thickness, damage degree and loading rate can be obtained to guide the stability design and stability prediction of the bearing structure.

[0136] The experimental model of the tunnel surrounding rock layered bearing structure is finally a cube with a side length of 30 cm. Figure 3 The layered bearing structure of the tunnel surrounding rock is as follows from the inside to the outside: fracture layer 1, plastic softening layer 2, elastic layer 3, original rock layer 4; the fracture layer 1, plastic softening layer 2, and elastic layer 3 are all in the shape of semicircular arches;

[0137] For example, in step S3, based on the mechanical properties test results, the relationship between the bearing capacity of the structure and the thickness of each layer, the degree of damage and the loading rate can be obtained, and finally the optimized layered bearing structure of the tunnel surrounding rock is obtained.

[0138] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for manufacturing and testing the performance of a tunnel surrounding rock layered bearing structure, characterized in that: The method comprises the following steps: S1, a method for making a layered bearing structure of tunnel surrounding rock based on 3D printing, making a model of the layered bearing structure of tunnel surrounding rock, constructing three-dimensional coordinates and performing 3D printing, and forming the model of the layered bearing structure of tunnel surrounding rock; designing a cross hollow body to represent the fracture damage, and distinguishing each layer by the volume proportion of the hollow body; S2, the mechanical properties of the formed tunnel surrounding rock layered bearing structure model are tested using the tunnel surrounding rock layered bearing structure performance testing method based on 3D printing; S3, based on the mechanical properties test results, the optimized layered bearing structure of the tunnel surrounding rock is obtained.

2. The method for manufacturing and testing the performance of the tunnel surrounding rock layered bearing structure according to claim 1 is characterized in that: In step S1, three-dimensional coordinates are constructed and 3D printing is performed, including: S101, classify the tunnel type and surrounding rock layer structure; determine the type of the model tunnel to be a semicircular arch tunnel, and take the inner wall of the tunnel as the starting point to divide the tunnel surrounding rock into a fracture layer, a plastic softening layer, an elastic layer and an original rock layer; S102, determine the basic parameters of the tunnel surrounding rock layer bearing structure, the fracture layer parameters are: thickness h1, vertical wall height h b , radius of semicircular arch r1, damage degree D1; The parameters of the plastic softening layer are: thickness h2, damage degree D2; The elastic layer parameters are: thickness h3; The original rock layer parameters are: thickness is h4; S103, testing the mechanical properties of the tunnel surrounding rock mass; S104, construction of a three-dimensional coordinate system; S105, representation of damage to the fractured layer and the plastic softening layer; using a computer to construct a three-dimensional coordinate system, a three-dimensional coordinate system is established according to the actual size of the tunnel surrounding rock layered bearing structure model, and the three-dimensional construction of the overall outline of the tunnel surrounding rock layered bearing structure model is completed; multiple cross hollow bodies are used to represent the cracks in the layered structure, and the damage calculation formula of the fractured layer and the plastic softening layer is: Where D f is the sum of the volumes of the cross hollow bodies, D m is the overall volume of each structural layer; S106, production of rupture layer; S107, plastic softening layer production; S108, elastic layer preparation; S109, made from original rock layers; S110, preparation of the layered bearing structure model of the surrounding rock of the overall tunnel.

3. The method for manufacturing and testing the performance of the tunnel surrounding rock layered bearing structure according to claim 2 is characterized in that: In step S103, the mechanical properties of the tunnel surrounding rock mass are tested, including: taking samples of the surrounding rock mass to be studied in each layer for uniaxial compression test, and determining the damage variable ranges of the elastic stage and the plastic softening stage according to the stress-strain and damage calculation formula: 0-D1 is the damage variable range of the elastic zone, D1-D2 is the damage variable range of the plastic softening zone, and D1-1 is the damage variable range of the rupture zone; The damage variable calculation formula is: Where E is the real-time elastic modulus of rock, and E0 is the initial elastic modulus of rock.

4. The method for manufacturing and testing the performance of a tunnel surrounding rock layered bearing structure according to claim 2 is characterized in that: In step S106, the preparation of the rupture layer includes: S1061, assuming that the damage of the rupture layer is D1, the volume of the cross hollow body is v1, and the number of cross damaged bodies is n1, then the damage of the rupture layer is: S1062, design cross hollow bodies evenly distributed in the layered structure; S1063, determining the printing materials of the fracture layer rock, the printing materials include: river sand, ordinary P.O425 cement, water, water glass and water reducing agent, and the ratio of printing materials for different lithology rock masses needs to be determined in combination with the physical and mechanical properties of the actual rock masses; S1064, three-dimensional spatial marking of the rupture layer boundary and cross damage volume; S1065, cross-lesion body print.

5. The method for manufacturing and testing the performance of the tunnel surrounding rock layered bearing structure according to claim 2 is characterized in that: In step S107, the plastic softening layer production includes: S1071, assuming that the damage of the plastic softening layer is D2, the volume of the cross hollow body is v2, and the number of cross damaged bodies is n2, then the damage of the plastic softening layer is: S1072, the cross hollow body distribution design is similar to the rupture layer, and the number is reduced relative to the rupture layer; S1073, determining the printing material of the plastic softening layer rock; S1074, three-dimensional spatial marking of the plastic softening layer boundary and cross damage.

6. The method for manufacturing and testing the performance of a tunnel surrounding rock layered bearing structure according to claim 2 is characterized in that: In step S108, the elastic layer manufacturing includes: S1081, determining the printing material of the elastic layer rock; S1082, determining the elastic layer boundary according to the structural parameters in S102, and performing three-dimensional space marking; In step S109, the original rock layer production includes: S1091, determine the printing material of the original rock layer; S1092, the arc-shaped lower boundary of the original rock layer coincides with the arc-shaped upper boundary of the elastic layer, and the outer boundary of the vertical wall of the original rock layer coincides with the inner boundary of the vertical wall of the elastic layer; In step S110, the overall model making includes: printing and molding through a sand mold 3D printer according to the constructed three-dimensional coordinates of the tunnel surrounding rock layered bearing structure model; using it for mechanical property testing after room temperature curing; printing parameters include the Z-AXIS value of the distance between the nozzle and the printing platform, the printing layer thickness, the printing speed and the printer filling rate; firstly, the printing Z-AXIS value is determined according to the comprehensive test of the specimen molding speed and molding accuracy under different Z-AXIS values, and then the printing layer thickness of 1.0mm~3.0mm and the printing speed of 150mm~300mm are determined according to the printer performance and the coarseness of the material; the filling method of the print selects the printer default filling rate.

7. The method for manufacturing and testing the performance of a tunnel surrounding rock layered bearing structure according to claim 1, characterized in that: In step S2, the mechanical properties test using the tunnel surrounding rock layered bearing structure performance test method based on 3D printing includes: S201, placing the model on a biaxial loading test bench without any support, and applying hydrostatic pressure to a predetermined value; S202, applying axial stress at a loading rate until the layered bearing structure of the tunnel surrounding rock is destroyed, and monitoring the stress-strain changes during the loading process; S203, changing the layer thickness or damage degree, loading rate conditions, and repeating the above experimental steps; S204, according to the monitored stress and deformation of each load-bearing layer and the sample as a whole, the stress and strain of the maximum load-bearing of the structure as a whole are obtained, and the load-bearing performance of the layered load-bearing structure is obtained; S205, according to the maximum bearing strength and ultimate deformation of the layered bearing structure of the tunnel surrounding rock under different parameters of layer thickness, damage degree and loading rate, each parameter is used as the horizontal coordinate and the maximum bearing strength or ultimate deformation of the structure is used as the vertical coordinate to obtain the relationship between the bearing capacity of the structure and each layer thickness, damage degree and loading rate.

8. The method for manufacturing and testing the performance of a tunnel surrounding rock layered bearing structure according to claim 7 is characterized in that: In step S201, strain gauges (501) are respectively attached to the surfaces of the fracture layer, plastic softening layer, elastic layer and original rock layer of the tunnel surrounding rock layered bearing structure model, and then connected to a static strain monitor (5) for deformation monitoring; In step S202, the loading rate is 0.06 mm / min.

9. A tunnel surrounding rock layered bearing structure, characterized in that: The structure is manufactured using the tunnel surrounding rock layered bearing structure manufacturing and performance testing method described in any one of claims 1 to 8. The structure comprises, from the inside to the outside, a fractured layer (1), a plastic softening layer (2), an elastic layer (3), and an original rock layer (4); the fractured layer (1), the plastic softening layer (2), and the elastic layer (3) are all in the shape of semicircular arches; and the original rock layer (4) is a cube.

10. The tunnel surrounding rock layered bearing structure according to claim 1, characterized in that: Strain gauges (501) are also pasted at different positions of the fracture layer (1), the plastic softening layer (2), the elastic layer (3), and the original rock layer (4), and then connected to a static strain monitor (5) for deformation monitoring.

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