A similar material for tunnel lining model extrusion 3D printing

Abstract

The application discloses a similar material for tunnel lining model extrusion type 3D printing. The similar material comprises the following components in parts by weight: quartz sand 35.03-35.38 parts; barite powder 8.76-11.1 parts; silica ash 18.43-32.84 parts; fly ash 21.89-36.85 parts; fiber 0.1-0.3 parts; fast hardening cement 0.12-0.99 parts; Portland cement 0.17-1.11 parts; water reducing agent 0.1-0.8 parts. The application selects standard sand, barite powder, silica ash and fly ash as aggregate under lower cement content, with ordinary cement and fast hardening cement as cementing material, and through a large number of experimental proportioning, obtains the lining similar material capable of being subjected to extrusion type 3D printing, which has good extrudability, constructability, adjustable mechanical parameters and certain toughness.

Description

TECHNICAL FIELD

[0001] The present application relates to 3D printing and rock mass engineering technology, in particular to a similar material for extrusion 3D printing of a tunnel lining model. BACKGROUND

[0002] At present, there are many tunnels under construction and to be newly built in China. In underground engineering, lining structure plays an important role in preventing deformation or collapse of surrounding rock, so it is necessary to study the stress characteristics and stability of lining structure in complex geological environment. In the study of underground engineering structure, the similarity theory is often used to scale down the prototype of underground structure, and a similar model of surrounding rock and lining structure is constructed to explore the mechanical response characteristics of the model under different loading environments, providing a theoretical basis for engineering design, construction and maintenance. With the progress of underground engineering technology, engineering and technical personnel design many irregular lining structures such as city gate arch, three-center arch, horseshoe arch, etc. Irregular lining structure puts forward new requirements for the preparation of similar models.

[0003] At present, the lining used in geological model experiment is mostly formed by template pouring. This construction method has the advantages of simple process and fast construction speed in engineering, but it cannot take advantage of template pouring in the process of geological model pouring. First of all, the core of this construction method is prefabricated template, and the precision and support rigidity of the template are directly related to the quality of the model. The cost of template manufacturing and processing for large-scale and high-precision lining model is very high. Moreover, the template has very low reusability, and different structural forms of lining structure required in the experiment need to be separately manufactured. Secondly, in order to ensure the compactness of the slurry, it is necessary to insert, vibrate and agitate during the template pouring process. In the narrow and deep pouring space of the lining template, the pouring quality is difficult to control. Finally, the template removal process after the model is poured and cured is very complicated. The rigid template is heavy, and the removal process is easy to damage the model. The flexible template is light, but its rigidity is low, which cannot meet the forming precision requirements of the lining model.

[0004] Compared with the above problems, 3D printing of tunnel lining model does not exist, and various structural forms and size characteristics of lining model can be easily prepared to realize the fine preparation of irregular lining structure for geological model. However, the similar material for powder 3D printing has low printing efficiency and small printing scale, and the existing extrusion 3D printing material only meets the requirements of 3D printing and cannot meet the similarity requirements. So far, there is no similar material for 3D printing extrusion process of tunnel lining model, so a similar material for high-efficiency large-scale 3D printing of tunnel lining model is urgently needed. This similar material meets the strict requirements of extrusion 3D printing, such as extrusion, buildability and setting time, so that the experimental results are more consistent with the actual situation. SUMMARY

[0005] The application aims to provide a similar material for tunnel lining model extrusion 3D printing, which can print various irregular lining structure models and is used for making a true lining structure physical model.

[0006] To achieve the above-mentioned purpose, the application adopts the technical scheme of:

[0007] A similar material for tunnel lining model extrusion 3D printing, which comprises the following components in parts by weight:

[0008] 35.03-35.38 parts of quartz sand, 8.76-11.1 parts of barite powder, 18.43-32.84 parts of silica ash, 21.89-36.85 parts of fly ash, 0.1-0.3 parts of fiber, 0.12-0.99 parts of fast hardening cement, and 0.17-1.11 parts of silicate cement.

[0009] The material further comprises an aqueous solution of water-reducing agent, and the amount of the aqueous solution of water-reducing agent is such that the fluidity of the material is 19 cm to 22 cm.

[0010] Preferably, the mass ratio of the related substances in the similar material is: barite powder / quartz sand = 0.25, (quartz sand + barite powder) / (silica ash + fly ash) = 0.80.

[0011] Preferably, the specific gravity of the barite powder is 4.51, and the particle size is less than 45 μm; the specific gravity of the quartz sand is 2.67, and the particle size is less than 0.42 mm; the specific gravity of the fly ash is 2.26; and the fiber is a fiber that can be cut and polished without producing dust.

[0012] Preferably, the fiber is a polypropylene fiber with a length of 12 mm; the fast hardening cement is a high belite sulphoaluminate cement; the water-reducing agent is a polycarboxylic acid water-reducing agent with a minimum water-reducing rate of 30%; and the fineness of the fly ash is 12% of the residue on a 45 μm square hole sieve.

[0013] Preferably, the similar material for tunnel lining model extrusion 3D printing has a fluidity of 19.2 cm to 21.6 cm, an initial setting time of 2.2 h to 4.9 h, and a construction height of not less than 40 cm.

[0014] Further, the similar material has similar mechanical properties to the lining model, and the density of the similar material is 21.4 g / cm 3 ~ 23.2 g / cm 3, the compressive strength is 473.4kPa~1804.6kPa, the elastic modulus is 371.8MPa~1332.9MPa, the tensile strength is 45.1kPa~128.4kPa, and the ratio of the compressive strength to the tensile strength is between 8.55~15.91; meet the needs of similar materials for C20, C30, C40 grade concrete lining in the range of geometric similarity scale 1 / 30~1 / 100.

[0015] The process of printing the lining model by using the similar material is:

[0016] According to the weight ratio, the quartz sand 35.03-35.38 parts, the barite powder 8.76-11.1 parts, the silica ash 18.43-32.84 parts, the fly ash 21.89-36.85 parts, the fiber 0.1-0.3 parts, the fast hardening cement 0.12-0.99 parts, and the portland cement 0.17-1.11 parts are weighed;

[0017] The quartz sand, the silica ash, the fly ash, the barite powder, the fast hardening cement, the portland cement and the fiber are mixed and stirred uniformly to obtain a mixture a;

[0018] The water reducing agent is mixed with water and stirred uniformly, the solid content of the water reducing agent is 4%, and a mixed solution b is obtained;

[0019] The mixed solution b is gradually poured into the mixture a, and the flow degree is measured in time during the stirring process after the mixed solution b is gradually added; if the flow degree reaches 19-22cm, the adding of the mixed solution is stopped, and a mixed material is obtained;

[0020] The obtained mixed material is put into the feeding module of the extrusion type 3D printing equipment, and then a model is printed on the test table;

[0021] After the model is precisely cut and polished by the subtractive mechanical arm, a finished product with a smooth surface is obtained after film curing for 14-28 days under room temperature conditions.

[0022] The height of the lining model printed by using the similar material is not less than 500mm, the lining model presents elastic-plastic failure characteristics, and the lining axial force and the bending moment are symmetrical along the loading axis.

[0023] Compared with the prior art, the present application has at least the following beneficial effects:

[0024] The similar material of the present application can be used for large-scale 3D extrusion printing by using two kinds of cement as cementing materials, cooperating with quartz sand, barite powder, fly ash and fiber, and through a large number of experimental proportions, the lining similar material with good extrudability, buildability and adjustable mechanical parameters is obtained, which meets the similarity requirement and is suitable for 3D printing of irregular structure lining.

[0025] The construction height of the similar material of the present application is not less than 40 cm, preferably 40 cm-50 cm, and at a lower cement content, the similar material printed test piece does not deform and twist at a higher construction height, so that the present application achieves higher construction at a lower strength ratio to meet the strength, elastic modulus and the like of the similar material, and realizes the demand of large-scale printing.

[0026] The formula of the similar material of the present application has a synergistic effect and mutual support among the components, meets the 3D extrusion printing requirement, and can ensure that the printed lining model is polished smoothly, is environmentally friendly in construction, does not produce a large amount of dust, and the printed circular lining model uses radial point load to test the mechanical properties, the load process, the lining presents elastic-plastic failure characteristics, and the lining axial force and bending moment are symmetrical along the loading axis, the model is homogeneous inside and has no obvious defects.

[0027] The raw materials used in the present application are few in kind, low in price and wide in source, fill the gap of the preparation technology of the similar material of the extrusion type 3D printed lining, have high printing efficiency and large printing scale, and the lining model has high toughness. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some examples of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0029] Figure 1 The appearance photos of the raw materials for printing the lining, wherein (a) is high belite sulphoaluminate cement; (b) is composite portland cement; (c) is quartz sand; (d) is fly ash; (e) is silica fume; (f) is polypropylene fiber

[0030] Figure 2 The path diagram of additive and subtractive material printing, wherein (a) is the additive material printing path; the additive material path spirally climbs from the bottom layer at a fixed angle and speed; (b) is the subtractive material printing path inside the lining; (c) is the subtractive material printing path outside the lining, which presents the printing path of gradually reducing the diameter of the lining model outside layer by layer from outside to inside.

[0031] Figure 3 The physical diagrams of different stages in the printing process of the lining model, wherein (a) is the physical diagram in the additive material printing process of the lining; (b) is the physical diagram of the additive material forming model; (c) is the physical diagram in the subtractive material printing process of the lining; (d) is the physical diagram of the additive and subtractive material printing finished product of the lining model.

[0032] Figure 4Figure for radial point load test of lining model.

[0033] Figure 5 Figure for radial point load test of lining model. DETAILED DESCRIPTION

[0034] For the purpose, technical solutions and advantages of the present application, the present application will be further described in detail with examples. However, it should be understood that the examples herein are only used to explain the present application, and are not used to limit the protection scope of the present application.

[0035] The present application is a similar material for tunnel lining model extrusion 3D printing. The test scheme of the embodiment of the present application is to analyze the similar material ratio by adjusting the mass of other materials under the premise that the mass of quartz sand and barite powder is unchanged. The experiment includes uniaxial compression test, splitting test, fluidity test and setting time test. Through the above tests, the uniaxial compressive strength, tensile strength, elastic modulus, setting time, fluidity and other mechanical parameters of the similar material are obtained. And according to different actual working conditions, a group of ratio schemes with the most ideal physical properties are selected to carry out the geological model test.

[0036] Specifically, the test design is as follows:

[0037] The experiment is designed by using orthogonal experiment method, see Table 1, the influencing factors include the mass ratio of quick-hardening cement to total cement, the mass ratio of silica fume to fly ash, the mass ratio of cementitious materials to aggregate, and the mass ratio of fiber to aggregate plus cementitious materials. There are four factors and three levels, a total of nine groups of tests. The similar material ratio of each group is shown in Table 2.

[0038] The experimental materials include quartz sand, silica fume, fly ash, barite powder, fiber, cement, quick-hardening cement, water reducing agent and water.

[0039] Specifically, the fiber is polypropylene fiber.

[0040] Specifically, the quick-hardening cement is high belite sulphoaluminate cement.

[0041] Specifically, the water reducing agent is polycarboxylic acid water reducing agent.

[0042] Specifically, the selected barite powder has a specific gravity of 4.51 and a particle size of less than 45 μm.

[0043] Specifically, the selected quartz sand has a specific gravity of 2.67 and a particle size of less than 0.42 mm.

[0044] Specifically, the selected fly ash has a specific gravity of 2.26 and a fineness of 45 μm square hole sieve residue of 12%.

[0045] The appearance of high belite sulfoaluminate cement, composite silicate cement, quartz sand, fly ash, silica fume, and polypropylene fiber is shown in the figure. Figure 1 .

[0046] The process of printing the lining model using the similar material in this invention is as follows:

[0047] Weigh out silica sand, silica fume, fly ash, barite powder, high belite sulfoaluminate cement, silicate cement, and fiber, mix and stir evenly to obtain mixture a.

[0048] Water and water-reducing agent are mixed and stirred evenly to obtain a mixed solution b with a water-reducing agent solid content of 4%.

[0049] Add mixture b to mixture a in 5ml increments, stirring thoroughly after each addition. Measure the flowability of the mixture while stirring, and stop adding the mixture when the flowability reaches 19-20cm. The resulting mixture is relatively homogeneous and less prone to fiber clumping.

[0050] The resulting mixture was placed into the feeding module of an extrusion 3D printing machine, and then the model was printed on the test bench. During the printing process, additive and subtractive printing paths were set. The additive printing path spiraled upwards from the bottom layer at a fixed angle and speed (see...). Figure 2 Figure (a) in the middle Figure 3 (as shown in Figure (a)) Figure 3 Figure (b) shows the additively formed model obtained after additive printing; the subtractive printing path includes the subtractive printing path on the inner side of the lining and the subtractive printing path on the outer side of the lining. The subtractive printing path on the inner side of the lining (see Figure 1) Figure 2 As shown in Figure (b), the process involves subtracting material from the inner side of the lining model layer by layer, with the diameter gradually increasing from the inside out. The robotic arm moves from top to bottom during the subtraction process. The subtraction printing path on the outer side of the lining (see Figure (b)) is also shown. Figure 2 As shown in Figure (c), the printing path involves subtracting material from the outer side of the lining model layer by layer, with the diameter gradually decreasing from the outside to the inside. The robotic arm moves from top to bottom during the subtraction process. See Figure (c) for details on the subtraction printing process of the outer lining. Figure 3 Figure (c) shows the finished product obtained after the model is precision-machined by a subtractive robotic arm and then cured in a film at room temperature for 14-28 days (see Figure 1). Figure 3 (Figure d)

[0051] Effect Analysis:

[0052] The test specimen for the elastic modulus test of similar materials was a 50*100 cylindrical specimen. The mechanical properties of similar materials were tested according to the test method in SL / T 264-2020 "Test Procedure for Rocks in Water Conservancy and Hydropower Engineering". The test results are shown in Table 3.

[0053] The working performance of similar materials was tested according to the test method of concrete fluidity in the Standard Test Methods for Properties of Fresh Ordinary Concrete GB-T 50080-2016, and the experimental results are shown in Table 4.

[0054] The similar material setting test piece was tested according to the test method of concrete setting time in the Standard Test Methods for Properties of Fresh Ordinary Concrete GB-T 50080-2016, and the experimental results are shown in Table 4.

[0055] Table 1 Similar material orthogonal test factors and levels

[0056]

[0057]

[0058] Note: barite powder / quartz sand = 0.25, (quartz sand + barite powder) / (silica fume + fly ash) = 0.80.

[0059] Table 2 Similar material proportioning parts

[0060]

[0061] Note: all solid materials total 100 parts.

[0062] Table 3 Physical and mechanical properties of similar materials

[0063] Number Compressive strength / kPa Elastic modulus / MPa Density / (g / cm 3 )]]> Tensile strength / kPa 1 523.5 410.9 2.260 49.9 2 910.9 599.4 2.231 71.8 3 1388.5 1172.1 2.180 128.4 4 990.8 889.6 2.284 106.3 5 1540.4 1270.9 2.256 113.0 6 473.4 371.8 2.142 45.1 7 1804.6 1332.9 2.320 113.5 8 756.8 567.6 2.222 88.5 9 1097.7 806.8 2.166 86.0

[0064] Table 4 Similar material fluidity and setting time

[0065] Number Fluidity / cm Initial setting time / h 1 21.2 4.9 2 19.7 3.9 3 20.3 3.8 4 21.6 3.5 5 20.9 3.1 6 20.2 4.5 7 19.2 2.2 8 20.1 4.2 9 19.9 2.7

[0066] Through similar ratio conversion, the requirements of C20, C30, C40 and other grade concrete lining on similar materials in the geometric similarity scale of 1 / 30-1 / 100 can be met. Taking C30 concrete as an example, the compressive strength is 30 MPa, the elastic modulus is 30 GPa, and the density is 2.4-2.5 g / cm 3 , the geometric similarity scale is 1 / 30, the density similarity scale is 1, the ideal similar material mechanical parameters are compressive strength 1000 kPa, elastic modulus 1000 MPa, and density 2.4-2.5 g / cm 3 , and the 4th group of proportioning parameters in Table 3 are very close to them, i.e. the 4th group of proportioning parameters can be used for printing material configuration and model printing.

[0067] The 4th group of materials is used to print the lining model with a height of not less than 500 mm, and the radial point load test is used to test the mechanical properties of the printed circular lining model, and the test process is as follows Figure 4As shown, static loads are applied to the upper and lower contact points of the circular lining. The contact area is under tension, with a negative tensile axial force, while the area at the horizontal plane orthogonal to the vertical loading surface is under compression, with a positive compressive axial force. As the load gradually increases, the axial force continuously increases, as indicated by the change in the envelope line from green to red. Figure 5 As shown in (a). Similarly, when the contact area is under tension, the bending moment turns to the outside of the lining and is taken as a positive value; when the vertical loading surface is orthogonal to the horizontal plane, the bending moment turns to the outside of the lining and is taken as a negative value. As the load gradually increases, the bending moment value continuously increases, i.e., there is a change from green to red envelope line. During the test, the lining exhibits elastic-plastic failure characteristics, and the axial force and bending moment of the lining are symmetrical from left to right, indicating that the printed lining model is homogeneous, of high quality, and without defects, which can meet the requirements of similar model tests for the lining model.

[0068] Therefore, we can conclude that:

[0069] The advantages of the similar material of this invention are that it has good extrudability and constructability, making it suitable for 3D printing physical model tests; it has the characteristic of adjustable mechanical parameters, and by controlling the addition ratio of different materials, the mechanical properties parameters such as bulk density, tensile and compressive strength, and elastic modulus of the material can be changed within a certain range, making it suitable for lining model tests; the fiber gives the prepared lining model a certain toughness, allowing the lining model to produce greater deformation, and producing more ideal experimental results on the basis of satisfying the similarity principle.

[0070] Furthermore, this invention determines the composition of similar material formulations through extensive testing and screening, enabling similar materials to have good working performance. This overcomes the shortcomings of conventional lining model similar materials being unsuitable for 3D printing technology. By controlling the material ratio, the material flowability and extrudability are improved, resulting in printed lining blanks with uniform texture that are not prone to collapse or deformation.

[0071] The lining similarity material of this invention uses few types of raw materials, is widely available, environmentally friendly and energy-saving, highly economical, and easy to promote. The preparation method of the lining similarity material is simple, suitable for high-precision concrete 3D printing technology, and has a wide range of material proportions to meet the needs of physical model tests with different similarity ratios. Therefore, the similarity material of this application meets both similarity requirements and extrusion 3D printing requirements, enabling the printing of large-scale lining models. The produced models have high precision and stable mechanical properties, meeting the precision requirements of irregular lining models.

[0072] The foregoing is a summary and description of the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only the principles of the present application. Without departing from the spirit and scope of the present application, the present application can also have such changes and improvements, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A similar material for tunnel lining model extrusion 3D printing, characterized in that, The similar material comprises the following components in parts by weight: 35.03-35.38 parts of quartz sand; 8.76-11.1 parts of barite powder; 18.43-32.84 parts of silica ash; 21.89-36.85 parts of fly ash; 0.1-0.3 parts of fiber; 0.12-0.99 parts of fast hardening cement; and 0.17-1.11 parts of portland cement; The water-soluble water reducing agent is further added to the material, and the amount of the water-soluble water reducing agent is such that the fluidity of the material is 19-22 cm. The mass ratio of the related substances in the similar material is: barite powder / quartz sand = 0.25, and (quartz sand + barite powder) / (silica ash + fly ash) = 0.

80.

2. A similar material for tunnel lining model extrusion 3D printing according to claim 1, characterized in that, The specific gravity of the barite powder is 4.51, and the particle size is less than 45 μm; the specific gravity of the quartz sand is 2.67, and the particle size is less than 0.42 mm; the specific gravity of the fly ash is 2.26; and the fiber is a fiber that can be cut and polished without producing dust.

3. The similar material for tunnel lining model extrusion 3D printing according to claim 1, characterized in that, The fiber is a polypropylene fiber with a length of 12 mm; the fast hardening cement is a high belite sulphoaluminate cement; the water reducing agent is a polycarboxylic acid water reducing agent with a minimum water reducing rate of 30%; and the fineness of the fly ash is 12% of the sieve residue of a 45 μm square hole sieve.

4. The similar material for tunnel lining model extrusion 3D printing according to claim 1, characterized in that, The fluidity of the similar material for tunnel lining model extrusion 3D printing is 19.2-21.6 cm, the initial setting time is 2.2-4.9 h, and the construction height is not less than 40 cm.

5. The similar material for tunnel lining model extrusion 3D printing according to claim 1, characterized in that, The similar material has similar mechanical properties with the lining model, and the density of the similar material is 21.4g / cm 3 ~23.2g / cm 3 , the compressive strength is 473.4kPa~1804.6kPa, the elastic modulus is 371.8MPa~1332.9MPa, the tensile strength is 45.1kPa~128.4kPa, and the ratio of the compressive strength to the tensile strength is between 8.55~15.91; meet the requirements of similar materials for C20, C30, C40 grade concrete lining in the range of geometric similar scale 1 / 30~1 / 100.

6. A similar material for tunnel lining model extrusion 3D printing according to claim 1, characterized in that, The process of printing a lining model using the similar material is as follows: The quartz sand, barite powder, silica ash, fly ash, fiber, fast hardening cement, and portland cement are weighed according to the parts by weight ratio; The quartz sand, silica ash, fly ash, barite powder, fast hardening cement, portland cement, and fiber are mixed and stirred uniformly to obtain a mixture a; The water reducing agent is mixed with water and stirred uniformly, and the solid content of the water reducing agent is 4% to obtain a mixed solution b; The mixed solution b is gradually poured into the mixture a, and the fluidity is measured in time during the stirring process after the mixed solution b is gradually added. If the fluidity reaches 19-22 cm, the addition of the mixed solution is stopped, and a mixed material is obtained; The obtained mixed material is put into the feeding module of the extrusion 3D printing equipment, and then a model is printed on the test bench; After the model is precisely cut and polished by a subtractive mechanical arm, a finished product with a smooth surface is obtained after film curing at room temperature for 14-28 days.

7. A similar material for tunnel lining model extrusion 3D printing according to claim 6, characterized in that, The height of the lining model printed by the similar material is not less than 500 mm, the lining model presents elastic-plastic failure characteristics, and the lining axial force and bending moment are symmetrical along the loading axis.

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