3D printing filling joint sample preparation method for water rock environment

Abstract

The invention belongs to the technical field of marine civil engineering and water conservancy and hydropower, and particularly relates to a preparation method of a 3D printing filling joint sample for a water-rock environment, which comprises the following steps: carrying out water saturation and mechanical test on a sampled rock mass; determining the proportion of the rock-like material conforming to the bed rock softening coefficient through an orthogonal test; a PVA material and an ABS material are subjected to composite spinning process treatment, and novel 3D printing materials with different solubility are obtained by controlling the proportion; acquiring information such as the filler type and the relative position condition of the filling joint, and reconstructing the joint in a three-dimensional manner by utilizing CAD (Computer Aided Design); printing a filling joint model which is similar to a real filling joint in water dissolution and softening degree by adopting a novel material; and pouring the filling joint composite model by using slurry prepared from a rock-like material, and carrying out curing, demolding and maintenance to obtain the filling joint sample. The invention provides a powerful tool and means for deeply researching the expansion mechanism of the rock mass filling joint in the water rock environment, and the operability is high.

Description

Technical Field

[0001] The present invention belongs to the technical fields of marine civil engineering and water conservancy and hydropower, and particularly relates to a method for preparing a 3D printed filled joint specimen for a water-rock environment. Background Art

[0002] The rock mass on the sea erosion platform and the cliff is submerged at high tide and exposed at low tide. The repeated rise and fall of the water level causes the rock wall to be in the alternation of dry and wet states, which intensifies the weathering effect on the rock mass, causes the original cracks in the rock mass to further extend and connect with the primary bedding cracks, and accelerates the formation of dangerous rocks and the occurrence of local collapse phenomena. There are a large number of filled joints inside the natural coastal rock mass. The low strength and large deformation characteristics of the joints will weaken the overall strength of the rock mass. At the same time, the existence of the filling material will further affect the stability of the rock mass. However, the types of filling materials are diverse, their sensitivities to water-rock interaction are different, and the degrees of damage generated are also different. Therefore, strengthening the research on the mechanical properties of different filled joint rock masses under the water-rock environment is not only an important topic in the fields of rock mechanics and engineering geology, but also can provide more effective disaster prevention and mitigation technical support for the protection of the coastal geological environment and geological relics.

[0003] At present, there are many methods for preparing different types of filled joint specimens. The main methods are as follows:

[0004] First, filled joints are made by filling materials such as mortar and gypsum through pre-burying iron sheets or mica sheets. This method is simple and efficient, but there are certain limitations in the size and surface morphology of the prefabricated open joints. When the joint size is too large or the inserted sheet is not in a straight shape, it will be difficult to pull out the inserted sheet after the casting material solidifies; or by making a rock-like specimen mold for filled prefabricated cracks or making different components and combining the components into a filled joint making mold, but it will be limited by the mold and unable to adjust the position, roughness, dip, etc. of the cracks, and cannot meet the simulation of complex joints. The above-mentioned production of filled joints is relatively traditional and lacks somewhat in making complex situations. Moreover, in order to ensure that the filled joints can accurately simulate the hydro-mechanical properties of the rock mass under real water-rock interaction, the fluidity of the filling material often needs to be sacrificed, resulting in particularly difficult filling operations, thus affecting the accuracy and reliability of the model's simulation of real geological conditions.

[0005] Second, by means of the innovative application of 3D printing technology, a high-precision joint model is printed using a 3D printer and then poured with materials. Different types of filled joint specimens can be made by 3D printing different joint models, such as columnar joints filled with hidden joints, open and filled complex fractures, internally filled joints, and the preparation of rock-like specimens with single fractures that are open or closed. This method mainly utilizes the volatility of 3D printing materials, and then fills materials into the joints, or directly simulates using 3D printing materials. However, most 3D printing materials are either insoluble or completely soluble in water, making it difficult to reflect the process of the cementitious substance inside the filled joints dissolving and softening when encountering water, and also difficult to reflect the differences in the dissolution and softening of different fillers when encountering water.

[0006] In summary, the methods for preparing filled joint specimens in the water-rock environment are still lacking. In view of this, there is an urgent need to develop a specimen preparation technology that can simply and accurately reflect the hydro-mechanical properties of real filled joints to promote the in-depth study of the expansion mechanism of rock mass filled joints under the action of water-rock coupling. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing 3D printed filled joint specimens in the water-rock environment. This method conducts composite spinning process treatment on low-temperature water-soluble PVA materials and ABS materials to develop a new type of printing material that can reflect the hydro-mechanical properties of real filled joints. Then, the filled joints are reconstructed in 3D using CAD, and the filled joint models are printed in 3D using the new type of printing material, and the prepared rock-like material slurry is used for pouring to complete the preparation of the filled joint specimens. The technical solutions adopted are as follows:

[0008] A method for preparing 3D printed filled joint specimens in the water-rock environment, characterized by comprising the following steps:

[0009] Step 1: Conduct a saturated water test on the sampled rock sample, and conduct a uniaxial compression mechanical test on the treated rock sample to determine the strength softening coefficient of the bedrock after saturation with water and the solubility of the filled joints;

[0010] Step 2: Determine the number of factors and the number of levels for each factor, design an orthogonal experiment, calculate the material ratio, mix the materials evenly according to different ratios to prepare specimens, and conduct measurements to obtain the strength softening coefficient of the specimens, and determine the material ratio that meets the strength softening coefficient of the bedrock;

[0011] Step 3: Place the PVA slices and ABS slices in a vacuum drying oven for drying treatment. After drying, combine them in different proportions and add them to the A and B feeding hoppers of a two-component spinning machine respectively. The raw materials are melted into melt streams in the screw heating zone through the composite spinning process, metered by a metering pump and enter the spinning box, and finally are ejected from the spinneret and collected by a winding machine to obtain a new type of 3D printing material with different solubilities;

[0012] Step 4: Obtain the information on the filling joint filler type and relative position in the in-situ sampling area, reconstruct the joint using CAD in 3D, and export the 3D digital space model of the filled joint.

[0013] Step 5: Use the new 3D printing material obtained in Step 3 and print it using a 3D printer to obtain a filled joint model with a water saturation solubility similar to that of the real filled joint in Step 1.

[0014] Step 6: Combine the filled joint model in Step 5 with an iron mold to form a composite mold, pour the rock-like material slurry prepared in Step 2 into the composite mold, and continuously vibrate. After curing, demolding, and curing, complete the preparation of the filled joint specimen.

[0015] Preferably, in Step 2, water, quartz sand, yellow clay, and high-strength gypsum are selected as the materials for making the rock-like specimen, quartz sand is used as the aggregate, high-strength gypsum is used as the binder, and yellow clay is used as the water sensitivity regulator.

[0016] Preferably, the mass ratio of water, quartz sand, yellow clay, and high-strength gypsum is 3 - 4: 3.7 - 4.5: 0.1 - 0.2: 9.8 - 12. As a further preference, the mass ratio is 3.3: 4: 0.11: 10.78.

[0017] Preferably, the PVA chips selected in Step 3 are completely water-soluble at low temperature, and the material properties conform to the water temperature conditions of the engineering practice; the selected ABS material is insoluble.

[0018] Preferably, in Step 3, the drying temperature of the composite spinning process is 40 - 50 °C, the time is 4 - 6 hours, and vacuum treatment ensures complete removal of moisture; the temperature of the screw heating zone is 180 - 240 °C, the screw speed is 140 r / min to ensure sufficient melting and mixing of the two; the temperature of the spinning box is 220 - 240 °C to ensure the fluidity and stability of the melt filament during the spinning process; the winding speed is 800 m / min to ensure uniform collection and shaping of the filament.

[0019] Preferably, control the ratio of ABS to PVA materials to be between 0.1 - 1:1.

[0020] Preferably, the method for reconstructing the joint in 3D using CAD in Step 4 is as follows: Analyze the obtained joint surface information, extract the contour and import it into CAD software, and reconstruct the 3D model of the joint surface through steps such as widening, stretching, and rotating. Finally, export it as a file format recognizable by the printer software, such as an.stl format file, to ensure that the model can be imported into the printing software for printing.

[0021] Preferably, in step 5, the fused deposition modeling printing method is used, and the printing temperature is 180-210 °C to ensure the smooth extrusion and precise deposition of the material during the printing process.

[0022] Preferably, in step 6, the rock-like material slurry prepared in step 2 is poured into the composite mold, continuously vibrated, demolded after being cured for 24 h, and the specimen is placed in a constant temperature environment of 28 °C for 28 d. Then, the end face of the specimen is slightly polished with a grinding machine, and finally, a 3D printed through-filled joint specimen for the water-rock environment is prepared.

[0023] Compared with the prior art, the beneficial advantages of the present invention are as follows:

[0024] The present invention proposes an efficient preparation method for a filled joint rock mass specimen in a water-rock environment, innovatively combining the composite spinning technology and 3D printing technology. Through the composite spinning technology, the present invention processes low-temperature water-soluble PVA material and insoluble ABS material, develops a new 3D printing material that can reflect the hydro-physical properties of the filling in real rock masses, and its solubility can be controlled by adjusting the raw material ratio, reflecting the hydro-physical properties such as the dissolution and softening of the cementing substance inside the filled joint when encountering water. The present invention combines the automated and high-precision 3D printing technology to realize the production of different forms of filled joint models, optimizes the production process of the filled joint specimen, shortens the specimen preparation cycle, improves the preparation accuracy and simulation effect of the filled joint rock mass specimen to a certain extent, and provides a new solution for exploring the properties of filled joints in a complex water-rock environment. Description of the Drawings

[0025] Figure 1 It is a process flow chart of the method for preparing a 3D printed filled joint specimen for the water-rock environment of the present invention.

[0026] Figure 2 It is a process flow chart of the method for making a new 3D printing consumable of the present invention.

[0027] Figure 3 It is a schematic diagram of the device for making a through-filled joint specimen in the example of the present invention.

[0028] Figure 4 It is a schematic diagram of the device for making an internally filled double-joint specimen in the example of the present invention.

[0029] In the figure: 1. Iron mold; 2. Through-filled joint model with an opening of 2 mm; 3. Hard non-expandable fiber filament. 4. Internally filled joint model with an opening of 2 mm; 5. Internally filled joint model with an opening of 3 mm. Detailed Embodiments

[0030] The accompanying drawings are only for illustrative purposes and do not represent the actual size and dimensions of the product; it should be understood that the listed embodiments are not all the technical solutions of the present invention, but only a part of them. The present invention will be described in detail below with reference to specific drawings and embodiments. Some common knowledge in the drawings and embodiments may be omitted.

[0031] Embodiment 1

[0032] As Figure 1 、 Figure 3 shown, a method for preparing a 3D printed through-filled joint specimen for a water-rock environment includes the following steps:

[0033] Step 1: Taking the coastal erosion platforms and cliff rock masses distributed in the southeastern coast as the research object, first conduct mechanical tests to determine the basic mechanical properties of the research object, and then through orthogonal tests, select a suitable material ratio as the rock-like material for preparing the bedrock, including water, quartz sand, yellow clay, and high-strength gypsum, and conduct saturation and mechanical tests (both the saturation test and the mechanical test use conventional methods in the prior art), and compare whether the strength softening coefficient, related mechanical properties, etc. of the specimen are similar to the actual properties of the research object. The finally selected material ratio is water:quartz sand:yellow clay:high-strength gypsum = 3.3:4:0.11:10.78;

[0034] Step 2: According to the basic information of the joints in the research area, such as the aperture size, joint roughness, and relative position, etc., use CAD to reconstruct the joints in three dimensions, and finally construct a three-dimensional digital space model of the through-filled joint 2 with an aperture of 2 mm;

[0035] Step 3: Conduct a saturation test on the fillers in the research area to determine the solubility of the fillers, control the ratio of ABS and PVA materials, and obtain a material with a solubility similar to that of the real weak joint fillers inside the coastal erosion platform rock mass through composite spinning process. Specifically, as in Step 4, the finally obtained material ratio is 0.33.

[0036] Step 4: Place the low-temperature water-soluble PVA slices and ABS slices in a vacuum drying oven to remove moisture. As Figure 2 shown, the dried materials are respectively added to the two feeding hoppers A and B of the spinning testing machine according to the ratio, melted into melt streams in the screw heating zone, metered by a metering pump and then enter the spinning box body, and finally are ejected from the spinneret plate and collected by a winding machine to obtain a new 3D printing material;

[0037] Step 5: Add the obtained new 3D printing material into a 3D printer, import the three-dimensional digital space model of the through-filled joint 2 into the 3D printer, print the through-filled joint 2 model by using the fused deposition modeling printing method, and fix the filled joint model in an iron mold 1 through a rigid non-expandable fiber wire 3 to form a composite mold.

[0038] Step 6: Pour the slurry prepared according to the ratio in Step 1 into the composite mold, vibrate continuously, demold after curing for 24 h, place the specimen in a constant temperature environment of 28 °C for 28 d, and then slightly polish the end face of the specimen with a grinding machine to finally obtain a 3D printed through-filled joint specimen for the water-rock environment.

[0039] As Figure 3 shown, in this embodiment, the side length of the through-filled joint type rock specimen is determined to be 50 mm, and the height is determined to be 100 mm.

[0040] Example 2

[0041] Refer to Figure 4 , a preparation method of a 3D printed built-in filled double joint specimen for the water-rock environment. The difference between this method and Example 1 is that in Example 2, a joint three-dimensional digital space model with an opening of 2 mm for the built-in filled joint 4 and an opening of 3 mm for the built-in filled joint 5 is constructed. Among them, the joint model 4 simulates silty clay, and the joint model 5 simulates sediment. The ratios of ABS to PVA in the new 3D printing materials of the two fillers are 0.28 and 0.65 respectively. The fused deposition modeling method is used to print a filled joint model with a solubility similar to that of a real joint. Finally, through casting, curing, demolding, and curing, the preparation of the built-in filled double joint specimen is completed.

[0042] The remaining content of this embodiment is the same as that of Example 1 and will not be elaborated here.

[0043] Example 3

[0044] The selected material ratio is water: quartz sand: yellow clay: high-strength gypsum = 3: 3.7: 0.1: 9.8.

[0045] Other unmentioned content is the same as that in Example 1.

[0046] Example 4

[0047] The selected material ratio is water: quartz sand: yellow clay: high-strength gypsum = 3.5: 4.2: 0.15: 11.

[0048] Other unmentioned content is the same as that in Example 1.

[0049] Example 5

[0050] The selected material ratio is water: quartz sand: yellow clay: high-strength gypsum = 4: 4.5: 0.2: 12.

[0051] Other unmentioned content is the same as that in Example 1.

[0052] Certainly, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing 3D printed filled joint specimens for a water-rock environment, characterized in that It includes the following steps: Step 1: Conduct a water saturation test on the sampled rock samples, perform a uniaxial compression mechanical test on the treated rock samples, and determine the strength softening coefficient of the bedrock after water saturation and the solubility of the filled joints; Step 2: Determine the number of factors and the number of levels for each factor, design an orthogonal experiment, calculate the material ratio, fully and evenly mix the materials according to different ratios to prepare specimens, and conduct measurements to obtain the strength softening coefficient of the specimens, and determine the material ratio that meets the strength softening coefficient of the bedrock; Step 3: Place the PVA slices and ABS slices in a vacuum drying oven for drying treatment. After drying, combine them in different proportions and add them to the two feeding hoppers A and B of a two-component spinning machine respectively. The raw materials are melted into melt streams in the screw heating zone, metered by a metering pump and enter the spinning box, and finally are ejected from the spinneret and collected by a winding machine to obtain a new type of 3D printing material with different solubilities; Step 4: Obtain information on the type and relative position of the filled joint filling materials in the on-site sampling area, use CAD to reconstruct the joints in three dimensions, and export a three-dimensional digital space model of the filled joints; Step 5: Use the new type of 3D printing material obtained in Step 3, and use a 3D printer to print to obtain a filled joint model with a water solubility similar to that of the real filled joints in Step 1; Step 6: Combine the filled joint model in Step 5 with an iron mold to form a composite mold, use the rock-like material slurry prepared in Step 2 to pour the formed composite mold, and continuously vibrate. After curing, demolding, and curing, complete the preparation of the filled joint specimens.

2. The 3D printing and filling joint specimen preparation method for water-rock environment according to claim 1, wherein In Step 2, water, quartz sand, yellow clay, and high-strength gypsum are selected as the materials for making rock-like specimens. Quartz sand is used as the aggregate, high-strength gypsum is used as the binder, and yellow clay is used as the water sensitivity regulator.

3. A method for preparing a 3D printed filled joint specimen for a water-rock environment according to claim 2, characterized in that, The mass ratio of water, quartz sand, yellow clay, and high-strength gypsum is 3 - 4:3.7 - 4.5:0.1 - 0.2:9.8 - 12.

4. A method for preparing a 3D printed filled joint specimen for a water-rock environment according to claim 1, characterized in that, In Step 3, the selected PVA slices have complete water solubility at low temperature, and the material properties meet the water temperature conditions of the engineering practice; the selected ABS material is insoluble.

5. A method for preparing a 3D printed filled joint specimen for a water-rock environment according to claim 4, characterized in that, In Step 3, the drying temperature of the composite spinning process is 40 - 50°C, the time is 4 - 6 hours, and vacuum treatment ensures complete removal of moisture; the temperature of the screw heating zone is 180 - 240°C, the screw speed is 140 r / min; the temperature of the spinning box is 220 - 240°C; the winding speed is: 800 m / min.

6. A method for preparing a 3D printed filled joint specimen for a water-rock environment according to claim 5, characterized in that Control the ratio of ABS to PVA materials to be between 0.1 - 1:

1.

7. A method for preparing a 3D printed filled joint specimen for a water-rock environment according to claim 1, characterized in that, The method for reconstructing the joints in three dimensions using CAD in Step 4 is as follows: Analyze the obtained joint surface information, extract the contour and import it into CAD software, and reconstruct the three-dimensional model of the joint surface through steps such as widening, stretching, and rotating. Finally, export it as a file format recognizable by the printer software to ensure that the model can be imported into the printing software for printing.

8. A method for preparing a 3D printed filled joint specimen for a water-rock environment according to claim 1, characterized in that, In Step 5, the fused deposition modeling printing method is used, and the printing temperature is 180 - 210°C to ensure the smooth extrusion and precise deposition of the material during the printing process.

9. A method for preparing a 3D printed filled joint specimen for a water-rock environment according to claim 1, characterized in that, In Step 6, pour the rock-like material slurry prepared in Step 2 into the composite mold, continuously vibrate it, demold it after curing for 24 h, place the specimen in a constant temperature environment of 28 °C for 28 d, and then slightly polish the end face of the specimen with a grinding machine to finally obtain a 3D printed through-filled joint specimen for the water-rock environment.

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