Hard rock transparent similar material with specific porosity and preparation method

Abstract

The invention belongs to the field of preparation of hard rock transparent similar materials, and particularly relates to a hard rock transparent similar material with specific porosity and a preparation method. The method comprises the following steps: calculating the mass of each component according to the volume and porosity of the required hard rock transparent similar material and the density of the components; pretreating solid particles; cleaning fused quartz sand, preparing a cementing agent, mixing, performing injection molding and curing, and removing a pore-forming agent to obtain the hard rock transparent similar material with specific porosity. The obtained hard rock transparent similar material overcomes the defect that a material prepared in the prior art does not have permeability, and reliable experimental support is provided for revealing a rock mass permeability mechanism and optimizing an engineering seepage control strategy. Meanwhile, the preparation method is easy and convenient to operate, materials are easy to obtain, the preparation period is shortened, and the research efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of preparation of transparent similar materials for hard rock, specifically relating to a transparent similar material for hard rock with a specific porosity and its preparation method. Background Technology

[0002] Traditional rock mechanics experiments primarily rely on natural rock samples or artificially synthesized opaque materials, making it difficult to directly observe key processes such as internal crack initiation and evolution. They can only rely on indirect measurements, such as acoustic emission, strain gauges, or post-failure cross-section analysis, leading to incomplete data and limited understanding of rock failure mechanisms. Furthermore, the mineral composition and pore distribution of natural rocks are random, resulting in poor reproducibility of experimental results. The preparation of transparent hard rock analogs overcomes these shortcomings. By adjusting the composition and curing process, the elastic modulus, Poisson's ratio, and other mechanical parameters of the target rock can be accurately reproduced, ensuring experimental reproducibility. Their optical transparency allows researchers to monitor internal deformation and damage development in real time using digital image correlation (DIC), CT scans, and other technologies, providing a more intuitive research tool for the geotechnical engineering field.

[0003] However, existing methods for preparing transparent similar materials for hard rock mainly fall into two categories: the first uses epoxy resin, curing agent, and saturated alcohol-rosin solution, resulting in high transparency but lacking anisotropy; the second uses quartz sand or glass sand as aggregate, and epoxy resin and curing agent as binders to fill the pores, resulting in lower transparency but more closely resembling the mechanical properties of natural rock. Current preparation methods primarily focus on simulating mechanical properties, and the resulting similar materials lack permeability. This missing key parameter limits their application in fluid-rock interaction studies, such as hydraulic fracturing in shale gas extraction and seepage in geothermal reservoirs. There is an urgent need to develop hard rock materials that combine transparency and controllable permeability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a transparent hard rock similar material with a specific porosity and a preparation method thereof. This method achieves precise control of the porosity of the transparent hard rock similar material within the range of 10%-40%, and the pore structure is uniformly distributed.

[0005] A transparent, similar material for hard rock with a specific porosity comprises fused silica sand, a binder, and a pore-forming agent. The binder is epoxy resin and a curing agent, and the pore-forming agent is sodium chloride. The porosity is 10%-40%. The specific preparation method is as follows: (1) Calculate the mass of each component based on the required volume and porosity of the transparent hard rock similar material and the density of the above components. The volume of the solidified transparent hard rock preform is V, and the volume of the fused silica sand and binder is V. 岩 The mass is m 岩 The volume of sodium chloride is V. 氯 The mass is m氯 The porosity of the target material is Φ, and the mass ratio of the binder to the fused silica sand is α, wherein the mass ratio of the binder to the fused silica sand is 15%-20%; the calculation formula is as follows: Φ= V 氯 / V; V = V 氯 +V 岩 m 氯 = ρ 氯 V 氯； ; m 石 =ρ 岩 V 岩 / (1+α) m 胶= α m 石 ; (2) Solid particle pretreatment: Wash the fused silica sand, dry the fused silica sand and sodium chloride and sieve them separately, mix the sieved fused silica sand and sodium chloride evenly to obtain solid particles; (3) Preparation of adhesive: Stir epoxy resin and curing agent evenly until transparent and free of flocculation to obtain adhesive; (4) Mix the binder and solid particles evenly to obtain a transparent hard rock premix; (5) Molding and curing: Apply petroleum jelly to the surface of the silicone mold for demolding. Fill the mold with the transparent hard rock premix obtained in step (4) in layers, vibrate while filling to remove excess air. After filling, smooth the surface and solidify at 25°C for 24 hours. Demold to obtain a transparent hard rock solidified embryo. (6) Remove the pore-forming agent: The transparent hard rock solidified embryo obtained in step (5) is rinsed in water for 24 hours, and the water is changed every 8 hours. After the sodium chloride is fully dissolved, it is dried at 25°C for 24 hours to obtain a transparent hard rock similar material with a specific porosity.

[0006] Preferably, in step (2), the ratio of the particle size of sodium chloride to the particle size of fused silica sand is 1:1.5-1:2. If the particle size is too small, the sodium chloride particles are easily wrapped by the fused silica sand skeleton, and water cannot pass through after solidification, resulting in poor pore connectivity. If the particle size is too large, the sodium chloride particles form isolated large pores after dissolving, resulting in low mechanical strength of the rock sample.

[0007] Preferably, the mass ratio of cementitious agent to fused silica sand in step (3) needs to be controlled at 15%-20%. If there is too little cementitious agent, the solid particles cannot be completely cemented together, resulting in the rock sample being unformed and brittle. If there is too much cementitious agent, the sodium chloride particles will be completely wrapped by the cementitious agent, and water cannot pass through after solidification, resulting in the inability to dissolve. In addition, during the solidification process, the cementitious agent will accumulate to the bottom of the mold due to gravity, resulting in the pores below the rock sample being completely filled, water cannot pass through, and it will not have porosity.

[0008] Preferably, the mass ratio of epoxy resin to curing agent in step (3) is 2:1-3:1.

[0009] Preferably, the curing agent in step (3) is polyetheramine.

[0010] Preferably, the mixing in step (4) should be completed within 30 minutes, otherwise the adhesive will heat up and solidify.

[0011] Pore-forming agents are divided into water-soluble pore-forming agents and high-temperature decomposition pore-forming agents. Most high-temperature decomposition pore-forming agents have a high degree of overlap with the thermal decomposition temperature of epoxy resin. Therefore, water-soluble pore-forming agents are used. The pore-forming agent used in this invention is sodium chloride, which has the following advantages: (1) Strong solubility: Compared with sulfates or other chlorides, sodium chloride has high solubility and can be quickly dissolved in water to avoid residues and does not produce by-products, such as urea releasing ammonia when dissolved in water; (2) Large particle size range: 0.05mm-5mm can be obtained by sieving or grinding. The uniform particles of mm allow for precise control of porosity, and the stable crystal structure makes it less prone to breakage during curing. In contrast, sodium sulfate is prone to absorbing moisture and clumping, sucrose is sticky and easily aggregates, and sodium bicarbonate is in powder form and is easily coated by binders, making it insoluble. (3) Easy to obtain and low cost: Industrial-grade sodium chloride is inexpensive and suitable for mass production. (4) Chemically inert: It does not react with other components and does not affect the curing process of the material, while alkaline salts such as carbonates will interfere with the curing and crosslinking of epoxy resin. (5) Environmentally friendly: The solution after dissolution is neutral and can be directly discharged or recycled. In summary, sodium chloride is selected as the pore-forming agent.

[0012] The beneficial effects of this invention are as follows: This invention provides a transparent hard rock similar material with specific porosity and its preparation method, filling the gap in previous studies that focused only on mechanical strength and neglected permeability in hard rock transparent similar materials. It provides a visual means for studying rock seepage mechanisms. This not only fills the gap in the simulation of seepage characteristics of existing hard rock transparent similar materials, but also provides reliable experimental support for revealing rock seepage mechanisms and optimizing engineering seepage control strategies. Furthermore, the preparation method is simple to operate, uses readily available materials, shortens the preparation cycle, and improves research efficiency. Attached Figure Description

[0013] Figure 1A flowchart illustrating a method for preparing a transparent similar material for hard rock with a specific porosity; Figure 2 The transparent hard rock specimen prepared for Comparative Example 1; Figure 3 The permeability of a hard rock transparent similar material with a porosity of 20% obtained in Example 1. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] Example 1 A transparent, hard rock-like material with a porosity of 20% and dimensions of 10 cm in height and 5 cm in diameter comprises fused silica sand, a binder, and a pore-forming agent. The binder is epoxy resin and a curing agent, the pore-forming agent is sodium chloride, and the curing agent is polyetheramine. The specific preparation method is as follows (e.g.) Figure 1 (as shown) (1) Calculate the mass of each component based on the required porosity and the density of each component. The mass ratio of the binder to the fused silica sand is 15%, and the mass ratio of the epoxy resin to the curing agent is 3:1. According to the calculation, 85.22g of sodium chloride, 264.99g of fused silica sand, 39.75g of binder, 29.81g of epoxy resin, and 9.94g of curing agent are required. (2) Solid particle pretreatment: Wash the fused silica sand, dry the fused silica sand and sodium chloride and sieve them separately. Use a sieve to sieve out fused silica sand with a particle size of 1-2 mm and sodium chloride with a particle size of 16-20 mesh. Mix the sieved fused silica sand and sodium chloride evenly to obtain solid particles. (3) Preparation of adhesive: Stir 29.81g of epoxy resin and 9.94g of curing agent until transparent and free of flocculation to obtain adhesive; during the stirring process, air should be avoided to prevent the formation of bubbles and reduction of transparency; (4) Mix the solid particles and cementitious agent in 5 batches until there are no dry particles agglomerating. Avoid mixing all at once, which may result in uneven distribution of cementitious agent and insufficient cementitious agent coating in some particles, leading to local loosening and reduced strength of the rock sample. The mixing time is 20 min; obtain transparent hard rock premix. (5) Molding and Curing: Apply Vaseline evenly to the inner surface of a silicone mold with an internal dimension of 10cm in height and 5cm in diameter to facilitate subsequent demolding. Fill the mold with the transparent hard rock premix obtained above, vibrating while filling to remove residual air bubbles. After all the above mixture has been filled, smooth the surface with a scraper, and let it stand at 25℃ for 24 hours to allow it to cure before demolding to obtain a transparent hard rock cured preform; (6) Remove the pore-forming agent: The transparent hard rock solidified embryo is rinsed in water for 24 hours with similar materials, and the water is changed every 8 hours. After the sodium chloride is fully dissolved, it is dried at 25°C for 24 hours. The hard rock transparent similar material with a porosity of 20% and a size of 10cm in height and 5cm in diameter is prepared.

[0016] Example 2: A hard rock transparent similar material with a porosity of 30% and dimensions of 10 cm in height and 5 cm in diameter includes fused silica sand, a binder, and a pore-forming agent. The binder is epoxy resin and a curing agent, the pore-forming agent is sodium chloride, and the curing agent is polyetheramine. (1) Calculate the mass of each component based on the required porosity and the density of each component. The mass ratio of the binder to the fused silica sand is 15%, and the mass ratio of the epoxy resin to the curing agent is 3:1. According to the calculation, 127.82g of sodium chloride, 231.86g of fused silica sand, 34.78g of binder, 26.08g of epoxy resin, and 8.70g of curing agent are required.

[0017] (2) The remaining steps are the same as in Example 1.

[0018] Comparative Example 1: A method for preparing a transparent hard rock similar material, as described in the paper "Experimental and Application Research on Physical and Mechanical Properties of Transparent Hard Rock Similar Materials": Epoxy resin and polyetheramine were mixed at a mass ratio of 3:1 and stirred continuously until the mixture changed from layering to turbidity and finally became a colorless and transparent liquid. The mass ratio of fused silica sand to the mixture was 3.25:1. The internal dimensions of the silicone mold were 10cm high and 5cm in diameter. The calculated mass of the mixture was 81.89g, and the mass of the fused silica sand was 266.14g. The mixture was poured into the silicone mold to the calculated mass, and then the weighed aggregate fused silica sand was added while stirring. After the fused silica sand was completely submerged in the mixture, the mold was placed in a vacuum degassing device and removed after 2 hours. Finally, it was placed in an electric heating drying oven at 25℃ and left for 36 hours. The prepared specimen was then removed using petroleum jelly as a release agent. The preparation was complete.

[0019] Figure 2The transparent hard rock specimens prepared using the above process have a dense and smooth surface. The gaps between the fused silica sand particles are fully filled by the binder, forming a continuous phase structure without pores, which results in the material not having the expected porosity characteristics.

[0020] Experimental Example 1: Using a triaxial rock testing system, the permeability of a hard rock transparent similar material with a porosity of 20% obtained in Example 1 was tested according to Darcy's formula at confining pressures of 5 MPa, 10 MPa, 15 MPa, 25 MPa, and 35 MPa, with pressure differential ratios of 0.2-0.8. Figure 3 As shown, the permeability of the prepared hard rock transparent similar material is on the order of 10. -18 m 2 The permeability range is consistent with that of natural low-permeability rocks such as sandstone and shale, indicating that the prepared hard rock transparent similar material has permeability.

Claims

1. A hard rock transparent similar material with a specific porosity, characterized in that, The mixture comprises fused silica sand, a binder, and a pore-forming agent, wherein the binder is epoxy resin and a curing agent, the pore-forming agent is sodium chloride, and the porosity is 10%-40%; the specific preparation method is as follows: (1) Calculate the mass of each component based on the required volume and porosity of the transparent hard rock similar material and the density of the above components. The volume of the solidified transparent hard rock preform is V, and the volume of the fused silica sand and binder is V. 岩 The mass is m 岩 The volume of sodium chloride is V. 氯 The mass is m 氯 The porosity of the target material is Φ, and the mass ratio of the binder to the fused silica sand is α; the calculation formula is as follows: Φ= V 氯 / V; V= V 氯 +V 岩 ; m 氯 = p 氯 V 氯 ; ； m 石 =p 岩 V 岩 / (1+a); m 胶= a m 石 ; (2) Solid particle pretreatment: Wash the fused silica sand, dry the fused silica sand and sodium chloride and sieve them separately, mix the sieved fused silica sand and sodium chloride evenly to obtain solid particles; (3) Preparation of adhesive: Stir epoxy resin and curing agent evenly until transparent and free of flocculation to obtain adhesive; (4) Mixing: Mix the binder and solid particles evenly to obtain a transparent hard rock premix; (5) Molding and curing: Apply petroleum jelly to the surface of the silicone mold, fill the mold with the transparent hard rock premix obtained in step (4) in layers, vibrate while filling to remove excess air, smooth the surface after filling, solidify at 25°C for 24 hours, demold to obtain the transparent hard rock solidified embryo. (6) Remove the pore-forming agent: The transparent hard rock solidified embryo obtained in step (5) is rinsed in water for 24 hours, and the water is changed every 8 hours. After the sodium chloride is fully dissolved, it is dried at 25°C for 24 hours to obtain a transparent hard rock similar material with a specific porosity.

2. The preparation method according to claim 1, characterized in that, In step (2), the ratio of the particle size of sodium chloride to the particle size of fused silica sand is 1:1.5-1:

2.

3. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of cementitious agent to fused silica sand is 15%-20%.

4. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of epoxy resin to curing agent is 2:1-3:

1.

5. The preparation method according to claim 1, characterized in that, The curing agent in step (3) is polyetheramine.

6. The preparation method according to claim 1, characterized in that, The mixing time in step (4) is ≤30 min.

7. A hard rock transparent similar material with a specific porosity obtained by the preparation method according to any one of claims 1-6.

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