Rock-like material containing micron-sized cracks and preparation method thereof

Abstract

The present application relates to the field of rock seepage testing, and specifically discloses a rock-like material containing micron-sized cracks and a preparation method thereof. The preparation method comprises the following steps: mixing quartz powder, a cementitious material, and an early strength agent to obtain a mixed dry material, wherein the cementitious material is a mixture of white Portland cement, silica fume, and amorphous nano-silicon dioxide; adding a portion of water to the mixed dry material and stirring, then increasing the stirring speed and adding a water reducer and the remaining water to obtain a slurry after mixing; pouring the slurry into a mold, pre-pressing it, and letting it stand, and then demolding it to obtain a sample; wrapping the sample with a water-insulating material and curing it in a dry environment to obtain a rock-like material containing micron-sized cracks. The prepared rock-like material has a micron-sized crack network and exhibits both high strength and brittle failure characteristics, providing the possibility and convenience for studying the seepage and failure characteristics of brittle hard rock under the action of seepage-force coupling.

Description

Technical Field

[0001] The present application relates to the field of rock seepage testing, and in particular to a rock-like material containing micron-sized cracks and a preparation method thereof. Background Art

[0002] As a natural geological body, rock has undergone long-term geological action during its formation, resulting in a large number of cracks of different scales inside it. These cracks will not only change the mechanical properties of the rock, but also affect the permeability of the rock, thereby affecting the durability of the rock structure. Accurately analyzing the influence of cracks on the permeability of rocks is of great significance for accurately evaluating the stability of rock masses. Therefore, many scholars have conducted rock seepage characteristic tests from different aspects. Natural rocks exhibit natural randomness and heterogeneity. If rock samples are obtained from natural rock masses by drilling cores, the repeatability of the test samples cannot be guaranteed, which affects the reliability and universality of rock seepage tests. Therefore, some scholars have proposed the use of artificial methods to prepare rock-like materials, and at the same time use different methods to prefabricate cracks to form rock-like materials with single or multiple cracks.

[0003] However, previous prefabricated fracture methods produce single, non-random fracture morphologies. Furthermore, the fracture openings are often on the millimeter scale, which is inconsistent with the micron- and even submicron-scale cracks found within natural rock, and certainly not the characteristics of a natural random fracture network. Furthermore, previously used resin-based materials exhibit extreme ductility during failure, which is inconsistent with the brittle failure characteristics of rock-based materials. While gypsum-based materials can simulate brittle failure, their low strength makes it difficult to simulate the mechanical properties of hard or extremely hard rock. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present application provides a rock-like material containing micron-sized cracks and a preparation method.

[0005] The present application provides a method for preparing a rock-like material containing micron-sized cracks using the following technical solution:

[0006] A method for preparing a rock-like material containing micron-sized cracks comprises the following steps:

[0007] Prepare the following raw materials by weight: 100-150 parts of quartz powder, 100 parts of cementitious material, 0.5-3 parts of early strength agent, 15-25 parts of water, and 0.5-1.5 parts of water reducer; wherein the cementitious material is a mixture of white Portland cement, silica fume powder, and amorphous nano-silicon dioxide;

[0008] Mixing quartz powder, gelling material and early strength agent to obtain mixed dry material;

[0009] Adding part of the water to the mixed dry material and stirring, then increasing the stirring speed and adding a water reducer and the remaining water, and mixing to obtain a slurry;

[0010] The slurry is poured into a mold, pre-pressed and allowed to stand, and demoulded to obtain a sample;

[0011] The sample is wrapped with a water-proof material and placed in a dry environment for curing to obtain a rock-like material containing micron-sized cracks.

[0012] Furthermore, the silica content of the quartz powder is greater than 95%, the particle size is 100 mesh to 300 mesh, and the moisture content is less than 0.1%.

[0013] Furthermore, in the cementitious material, the white silicate cement is 52.5R white silicate cement, the mass ratio of 52.5R white silicate cement to silica fume is 1:0.05-1:0.2, and the mass ratio of 52.5R white silicate cement to amorphous nano-silicon dioxide is 1:0.05-1:0.01.

[0014] Furthermore, the tricalcium silicate content of the 52.5R white Portland cement is greater than 60%.

[0015] Furthermore, the silicon dioxide content of the silica fume powder is greater than 95%, and the average particle size is less than 50 nm.

[0016] Furthermore, the silicon dioxide content of the amorphous nano-silica is greater than 99%, and the average particle size is less than 10 nm.

[0017] Furthermore, the early strength agent is a solid mixture of sodium metaaluminate and sodium silicate.

[0018] Furthermore, the water reducer is a polycarboxylic acid type liquid water reducer with a water reduction efficiency greater than 30%.

[0019] The inventive concept of this application is as follows:

[0020] Quartz powder acts as both a filler and an aggregate to provide skeleton support, ensuring the overall stability of rock-like materials.

[0021] White silicate cement with extremely high tricalcium silicate content is used. During the reaction process, the hydration reaction of tricalcium silicate will produce great chemical shrinkage, providing the original driving force for the subsequent tensile cracks.

[0022] The addition of silica fume and amorphous nano-silica reacts with calcium hydroxide, a hydration product of cement, to produce hydrated calcium silicate, enhancing overall strength. However, this reaction is accompanied by significant chemical shrinkage, further increasing the internal shrinkage and tensile forces of the system. The average particle size of silica fume is tens of nanometers, while that of amorphous nano-silica is only a few nanometers. Their significant difference in specific surface area significantly impacts fluidity. Therefore, a suitable blending ratio of silica fume and amorphous nano-silica is crucial to ensure both fluidity and strength, as well as appropriate shrinkage and deformation.

[0023] By using an extremely low water-cement ratio, the prepared rock-like material undergoes extreme self-drying shrinkage during the later reaction process, thereby forming a randomly distributed micron-scale crack network.

[0024] The addition of early strength agent can improve the early strength of the system, shorten the hydration process, reduce the sample preparation cycle, and greatly improve the test efficiency.

[0025] Furthermore, the water-proof material is a polyethylene-aluminum foil-nylon three-layer composite film, wherein the polyethylene is the inner layer, the aluminum foil is the middle layer, and the nylon is the outer layer.

[0026] The specimens are wrapped in a composite film. The inner polyethylene layer provides a good seal and humidity isolation, while the middle aluminum foil further blocks moisture penetration. The outer nylon layer has good toughness and mechanical properties, providing excellent protection for the specimen wrapping layer. Curing in a dry environment prevents moisture from escaping from the specimen, maintaining a uniform humidity level and eliminating uneven microstructural variations caused by evaporation. This makes it possible to obtain uniform and repeatable samples.

[0027] The present application also provides a rock-similar material containing micron-sized cracks, which is prepared using the above method. The rock-similar material contains a micron-sized crack network and can be used as a sample for seepage-force coupling tests.

[0028] In summary, this application has the following beneficial technical effects:

[0029] This method utilizes common raw materials or industrial solid waste to produce rock-like materials indoors, resulting in a random micron-scale crack network. The resulting material exhibits mechanical strength exceeding 100 MPa and exhibits significant brittleness during failure, meeting the requirements for simulating the internal crack network and mechanical properties of rock. This method not only addresses the difficulties of original rock sampling in seepage-mechanical coupling experiments, such as difficulty, high cost, unevenness, incompleteness, and poor representativeness, but also addresses the previous challenges of obtaining micron-scale crack networks, low strength, and significant ductility during failure in rock-like materials. This method provides both the possibility and convenience of studying the seepage and failure characteristics of brittle hard rock under seepage-mechanical coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic flow chart of a method for preparing a rock-like material containing micron-sized cracks according to an embodiment of the present application;

[0031] Figure 2 Schematic cross-sectional view of the mold in the embodiment of the present application, wherein (a) is the sample pressing process, and (b) is the sample demoulding process;

[0032] Figure 3 These are microscopic images of rock-similar materials prepared in the examples of this application, where (a) is Example 1, (b) is Example 2, and (c) is Example 3.

[0033] Figure numerals: 1, mold body; 2, through hole; 3, pad; 4, pressure rod; 5, pressure plate; 6, sample. DETAILED DESCRIPTION

[0034] The following is combined with Figure 1-3 This application is described in further detail.

[0035] Example 1

[0036] The present application discloses a method for preparing a rock-like material containing micron-sized cracks. Figure 1 , including the following steps:

[0037] Step 1: Prepare the following raw materials by weight: 100 parts of quartz powder, 100 parts of cementitious material, 1 part of early strength agent, 20 parts of water, and 0.5 parts of water reducing agent;

[0038] The quartz powder is high-purity quartz powder, with a silicon dioxide content greater than 95%, a particle size of 100-300 mesh, and a moisture content less than 0.1%;

[0039] The cementitious material is a mixture of 52.5R white Portland cement, silica fume and amorphous nano-silica, with the mass ratio of the components being: 52.5R white Portland cement: silica fume: amorphous nano-silica = 1:0.05:0.05; the tricalcium silicate content of the 52.5R white Portland cement is greater than 60%; the silica content of the silica fume is greater than 95% and the average particle size is less than 50 nanometers; the silica content of the amorphous nano-silica is greater than 99% and the average particle size is less than 10 nanometers;

[0040] The early strength agent is a solid mixture of sodium metaaluminate and sodium silicate in a ratio of 1:1;

[0041] The water reducer is a polycarboxylic acid type liquid water reducer with a water reduction efficiency greater than 30%.

[0042] Step 2: Mix the quartz powder, cementitious material and early strength agent, and stir slowly for 1 minute using a blender to obtain a uniform dry material.

[0043] Step 3: Add 75% of the water to the mixed dry materials and stir slowly for 1 minute; then add the water reducer and the remaining 25% of the water, stir rapidly for 2 minutes to obtain a slurry with a certain fluidity.

[0044] Step 4: Pour the slurry into the mold, pre-press it with a pressure of 5kN, let it rest for 1 hour, and then demould it to obtain the sample;

[0045] Reference Figure 2 The mold includes a mold body 1, a backing plate 3, and a force transmission component. The mold body 1 is cylindrical, closed at the bottom and open at the top, with a through hole 2 at the center of the closed bottom end. The backing plate 3 is circular and conforms to the contour of the cavity within the mold body 1. The force transmission component includes a fixedly connected pressure plate 5 and a pressure rod 4. The pressure plate 5 is circular and conforms to the contour of the cavity within the mold body 1. The cross-sectional profile of the pressure rod 4 conforms to the through hole 2 at the bottom of the mold body 1.

[0046] Before sample preparation, Figure 2 As shown in (a), the open end of the mold body 1 is placed upward, and the pad 3 is placed in the mold body 1 so that the pad 3 covers the through hole 2 at the closed end of the mold body 1; then the slurry is poured into the mold body 1, the pressing plate 5 is pressed against the upper surface of the sample 6, and the pressing rod 4 is connected to the press to apply pressure to the sample 6.

[0047] After standing for a while, Figure 2 As shown in (b), the open end of the mold body 1 is facing downward, and the pressure rod 4 is inserted into the through hole 2 at the closed end of the mold body 1 so that the end of the pressure rod 4 abuts against the pad 3; then the pressure plate 5 is connected to the press, and pressure is applied to push the sample 6 out of the mold body 1 to complete the demoulding.

[0048] Step 5: Wrap the sample with a polyethylene-aluminum foil-nylon three-layer composite film and place it in a drying dish for curing. The temperature is controlled at 25±0.5℃ to obtain a rock-like material containing micron-sized cracks.

[0049] Example 2

[0050] The embodiment of the present application discloses a method for preparing a rock-like material containing micron-sized cracks. The difference from Example 1 is that in step 1, the mass ratio of the components in the cementitious material is: 52.5R white silicate cement: silica fume powder: amorphous nano-silica = 1:0.1:0.05.

[0051] Example 3

[0052] The embodiment of the present application discloses a method for preparing a rock-like material containing micron-sized cracks. The difference from Example 1 is that in step 1, the mass ratio of the components in the cementitious material is: 52.5R white silicate cement: silica fume powder: amorphous nano-silica = 1:0.15:0.05.

[0053] Performance testing:

[0054] The rock-like materials prepared in Examples 1-3 were characterized by microscopic images. The results are as follows: Figure 3 As shown, density, compressive strength, flexural strength, crack density and average crack width tests were carried out. The test results are shown in Table 1:

[0055] Table 1 Test results of rock-like materials prepared in Examples 1-3

[0056]

[0057] from Figure 3 It can be seen that the rock-like material prepared in the examples of this application has a random micron-scale crack network with uniform crack distribution and width, meeting the requirements for simulating the internal crack network of rock. Furthermore, Table 1 shows that by adjusting the content of silica fume in the cementitious material, crack density and width can be regulated. When the silica fume content in the cementitious material increases, both the crack density and average crack width increase. This is because when the difference in content between large-particle silica fume and small-particle amorphous nano-silica increases, it helps to increase the shrinkage and tensile forces within the system.

[0058] As can be seen from Table 1, the rock-similar material prepared in the embodiment of the present application has a density close to that of natural rock, a compressive strength of more than 100 MPa, and exhibits obvious brittleness during the destruction process, which meets the requirements for simulating the mechanical properties of rock.

[0059] Using the rock-similar material prepared by the method of the present application as a specimen for the seepage-force coupling test not only improves the problems of difficulty, high cost, unevenness, incompleteness and poor representativeness of original rock sampling in the seepage-force coupling test, but also improves the previous problems of difficulty in obtaining micron-level crack networks, low strength and obvious ductility in the failure process of rock-similar materials, providing the possibility of studying the seepage and failure characteristics of brittle hard rock under the action of seepage-force coupling.

[0060] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing a rock-like material containing micron-sized cracks, characterized by: The following steps are involved: Prepare the following raw materials by weight: 100-150 parts of quartz powder, 100 parts of cementitious material, 0.5-3 parts of early strength agent, 15-25 parts of water, and 0.5-1.5 parts of water reducer; wherein the cementitious material is a mixture of white Portland cement, silica fume, and amorphous nano-silicon dioxide; in the cementitious material, the white Portland cement is 52.5R white Portland cement, the mass ratio of 52.5R white Portland cement to silica fume is 1:0.05-1:0.2, and the mass ratio of 52.5R white Portland cement to amorphous nano-silicon dioxide is 1:0.05-1:0.01; and the tricalcium silicate content of the 52.5R white Portland cement is greater than 60%; Mixing quartz powder, gelling material and early strength agent to obtain mixed dry material; Adding part of the water to the mixed dry material and stirring, then increasing the stirring speed and adding a water reducer and the remaining water, and mixing to obtain a slurry; The slurry is poured into a mold, pre-pressed and allowed to stand, and demoulded to obtain a sample; The sample is wrapped with a waterproof material, which is a polyethylene-aluminum foil-nylon three-layer composite film, wherein the polyethylene is the inner layer, the aluminum foil is the middle layer, and the nylon is the outer layer; and is placed in a dry environment for curing to obtain a rock-like material containing micron-sized cracks.

2. The method for preparing a rock-like material containing micron-sized cracks according to claim 1, characterized in that: The silica content of the quartz powder is greater than 95%, the particle size is 100-300 mesh, and the moisture content is less than 0.1%.

3. The method for preparing a rock-like material containing micron-sized cracks according to claim 1, characterized in that: The silicon dioxide content of the silica fume powder is greater than 95%, and the average particle size is less than 50 nm.

4. The method for preparing a rock-like material containing micron-sized cracks according to claim 3, characterized in that: The silicon dioxide content of the amorphous nano-silica is greater than 99%, and the average particle size is less than 10 nm.

5. The method for preparing a rock-like material containing micron-sized cracks according to claim 1, characterized in that: The early strength agent is a solid mixture of sodium metaaluminate and sodium silicate.

6. The method for preparing a rock-like material containing micron-sized cracks according to claim 1, characterized in that: The water reducing agent is a polycarboxylic acid type liquid water reducing agent with a water reducing efficiency greater than 30%.

7. A rock-like material containing micron-sized cracks, characterized by: The rock-like material is prepared by the preparation method according to any one of claims 1 to 6, and contains a micron-scale crack network.

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