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

Abstract

The invention relates to the field of rock seepage tests, and particularly discloses a micron-sized crack-containing rock similar material and a preparation method thereof, and the preparation method comprises the following steps: stirring and mixing quartz powder, a cementing material and an early strength agent to obtain a uniformly mixed dry material; wherein the cementing material is a mixture of white Portland cement, silica fume powder and amorphous nano silicon dioxide; adding part of water into the uniformly mixed dry material, stirring, then increasing the stirring speed, adding a water reducing agent and the balance of water, and uniformly mixing to obtain slurry; pouring the slurry into a mold, pre-pressing, standing, and demolding to obtain a sample; the sample is wrapped with a waterproof material and placed in a dry environment for maintenance, and the rock similar material containing the micron-sized cracks is obtained. The prepared rock similar material has a micron-sized crack network and also shows high strength and brittle failure characteristics, and provides possibility and convenience for researching seepage and failure characteristics of brittle hard rocks under the seepage-force coupling action.

Description

Technical Field

[0001] The present application relates to the field of rock seepage test, 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, and thus affect the durability of the rock structure. Accurately analyzing the influence of cracks on the permeability characteristics 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 show natural randomness and heterogeneity. If rock samples are obtained from natural rock masses by core drilling, the repeatability of the test samples cannot be guaranteed, which affects the reliability and universality of rock seepage tests. Therefore, some scholars have proposed to use artificial methods to prepare rock-like materials, and use different methods to prefabricate cracks to form rock-like materials with single or multiple cracks.

[0003] However, the cracks generated by the previous prefabricated crack methods have a single shape and are not random. At the same time, the opening of the cracks is often at the millimeter level, which is inconsistent with the micron-level or even submicron-level cracks inside natural rocks, and cannot meet the characteristics of natural random crack networks. In addition, the resin-based materials used in the past show great ductility during the destruction process, which does not meet the characteristics of brittle failure of rock materials. Although gypsum-based materials can simulate brittle failure, their strength is low and it is difficult to simulate the mechanical properties of hard rock or extremely hard rock. Summary of the invention

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

[0005] The present application provides a method for preparing a rock-like material containing micron-sized cracks using the following technical solution: A method for preparing a rock-like material containing micron-sized cracks comprises the following steps: 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 reducing agent; wherein the cementitious material is a mixture of white silicate cement, silica fume powder and amorphous nano-silicon dioxide; The quartz powder, the cementitious material and the early strength agent are stirred and mixed to obtain a mixed dry material; Adding part of the water to the mixed dry material and stirring, then increasing the stirring speed and adding a water reducing agent and the remaining water, and mixing to obtain a slurry; The slurry is poured into a mold, pre-pressed and allowed to stand, and a sample is obtained after demoulding; 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.

[0006] Furthermore, the silica content of the quartz powder is greater than 95%, the particle size is 100 mesh-300 mesh, and the water content is less than 0.1%.

[0007] 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 powder 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.

[0008] Furthermore, the tricalcium silicate content of the 52.5R white silicate cement is greater than 60%.

[0009] Furthermore, the silicon dioxide content of the silicon ash powder is greater than 95%, and the average particle size is less than 50nm.

[0010] Furthermore, the silicon dioxide content of the amorphous nano-silicon dioxide is greater than 99%, and the average particle size is less than 10 nm.

[0011] Furthermore, the early strength agent is a solid mixture of sodium aluminate and sodium silicate.

[0012] Furthermore, the water reducing agent is a polycarboxylic acid type liquid water reducing agent, and the water reducing efficiency is greater than 30%.

[0013] The inventive concept of this application is as follows: Quartz powder acts as both a filler and an aggregate to provide skeleton support, ensuring the overall stability of rock-like materials.

[0014] 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.

[0015] The introduction of silica fume and amorphous nano-silicon dioxide can react with calcium hydroxide, a cement hydration product, to produce hydrated calcium silicate, thereby improving the overall strength. At the same time, this reaction will be accompanied by a large chemical shrinkage, further increasing the shrinkage and tensile force inside the system. The average particle size of silica fume is tens of nanometers, while the average particle size of amorphous nano-silicon dioxide is a few nanometers. Their specific surface areas are very different, and their addition has a great impact on fluidity. Therefore, silica fume and amorphous nano-silicon dioxide need to be mixed in a suitable ratio to ensure both fluidity and strength and appropriate shrinkage deformation.

[0016] By using an extremely low water-cement ratio, the prepared rock-like material undergoes a great self-drying shrinkage during the later reaction process, thereby forming a randomly distributed micron-scale crack network.

[0017] 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.

[0018] Furthermore, the waterproof material is a three-layer composite film of polyethylene-aluminum foil-nylon, wherein the polyethylene is the inner layer, the aluminum foil is the middle layer, and the nylon is the outer layer.

[0019] The sample is wrapped with a composite film. The inner polyethylene layer can achieve good sealing and humidity isolation. The middle aluminum foil can further block the penetration of internal and external moisture. The outer nylon has good toughness and mechanical properties, which can better protect the sample wrapping layer. Curing in a dry environment can ensure that the moisture inside the sample does not overflow, fully maintain uniform humidity inside, eliminate the uneven distribution of moisture caused by internal moisture evaporation and the uneven internal microstructure, and provide the possibility of obtaining uniform and repeatable samples.

[0020] The present application also provides a rock-similar material containing micron-sized cracks, which is prepared by 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.

[0021] In summary, this application includes the following beneficial technical effects: The rock-like material prepared in the present application method using common raw materials or industrial solid waste materials has a random micron-level crack network, a mechanical strength of more than 100 MPa, and exhibits obvious brittleness during the destruction process, which meets the requirements of simulating the internal crack network and mechanical properties of the rock. It 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 problems of difficulty in obtaining micron-level crack networks, low strength, and obvious ductility in the destruction process of rock-like materials in the past, providing the possibility and convenience for studying the seepage and destruction characteristics of brittle hard rock under the action of seepage-force coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It 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; Figure 2 2 is a schematic cross-sectional view of a mold in an embodiment of the present application, wherein (a) is a sample pressing process, and (b) is a sample demoulding process; Figure 3These are microscopic images of rock-similar materials prepared in the examples of the present application, wherein (a) is Example 1, (b) is Example 2, and (c) is Example 3.

[0023] Figure numerals: 1. mold body; 2. through hole; 3. pad; 4. pressure rod; 5. pressure plate; 6. sample. DETAILED DESCRIPTION

[0024] The following is combined with Figure 1-3 This application is described in further detail.

[0025] Example 1 The present application embodiment discloses a method for preparing a rock-like material containing micron-sized cracks. Figure 1 , including the following steps: 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; The quartz powder is high-purity quartz powder, in which the silicon dioxide content is greater than 95%, the particle size is 100 mesh-300 mesh, and the moisture content is less than 0.1%; The cementitious material is a mixture of 52.5R white silicate cement, silica fume powder and amorphous nano-silicon dioxide, and the mass ratio of each component is: 52.5R white silicate cement: silica fume powder: amorphous nano-silicon dioxide = 1:0.05:0.05; the tricalcium silicate content of 52.5R white silicate cement is greater than 60%; the silica content of silica fume powder is greater than 95%, and the average particle size is less than 50 nanometers; the silica content of amorphous nano-silicon dioxide is greater than 99%, and the average particle size is less than 10 nanometers; The early strength agent is a solid mixture of sodium aluminate and sodium silicate in a ratio of 1:1; The water reducing agent is a polycarboxylic acid type liquid water reducing agent with a water reducing efficiency greater than 30%.

[0026] Step 2: Mix the quartz powder, cementitious material and early strength agent, and stir slowly for 1 minute using a mixer to obtain a uniformly mixed dry material.

[0027] 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.

[0028] Step 4: Pour the slurry into the mold, pre-press it with a pressure of 5 kN, let it stand for 1 hour, and then demould it to obtain a sample; Reference Figure 2The mold includes a mold body 1, a pad 3 and a force transmission component. The mold body 1 is cylindrical, closed at the bottom and open at the top, and a through hole 2 is opened at the center of the bottom closed end. The pad 3 is circular and matches the contour of the cavity in the mold body 1. The force transmission component includes a fixedly connected pressing plate 5 and a pressing rod 4, wherein the pressing plate 5 is circular and matches the contour of the cavity in the mold body 1, and the cross-sectional contour of the pressing rod 4 matches the through hole 2 at the bottom of the mold body 1.

[0029] 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 on the upper surface of the sample 6, and the pressing rod 4 is connected to the press to apply pressure to the sample 6.

[0030] 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 machine, and pressure is applied to push the sample 6 out of the mold body 1 to complete the demoulding.

[0031] 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°C to obtain a rock-like material containing micron-sized cracks.

[0032] Example 2 The embodiment of the present application discloses a method for preparing a rock-like material containing micron-sized cracks, which is different from Example 1 in 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-silicon dioxide = 1:0.1:0.05.

[0033] Example 3 The embodiment of the present application discloses a method for preparing a rock-like material containing micron-sized cracks, which is different from Example 1 in 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-silicon dioxide = 1:0.15:0.05.

[0034] Performance Test: Microscopic images of the rock-like materials prepared in Examples 1-3 were characterized, and the results were as follows: Figure 3 As shown, density, compressive strength, flexural strength, crack density and average crack width tests were carried out, and the test results are shown in Table 1: Table 1 Test results of rock-like materials prepared in Examples 1-3

[0035] from Figure 3 It can be seen that the rock-like material prepared in the embodiment of the present application has a random micron-scale crack network, and the distribution and width of the cracks are uniform, which meets the requirements of simulating the internal crack network of the rock. Further, it can be seen from Table 1 that by adjusting the content of silica fume in the cementitious material, the crack density and width can be regulated; when the content of silica fume in the cementitious material increases, the crack density and the average crack width both increase, because when the difference in the content of large-particle silica fume and small-particle amorphous nano-silicon dioxide increases, it helps to increase the shrinkage and tensile force inside the system.

[0036] It can be seen from Table 1 that 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 rock mechanical properties.

[0037] 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 problems of difficulty in obtaining micron-level crack networks, low strength and obvious ductility in the destruction process of rock-similar materials in the past, providing the possibility of studying the seepage and destruction characteristics of brittle hard rock under the action of seepage-force coupling.

[0038] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a rock-like material containing micron-sized cracks, Features: 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 reducing agent; wherein the cementitious material is a mixture of white silicate cement, silica fume powder and amorphous nano-silicon dioxide; The quartz powder, the cementitious material and the early strength agent are stirred and mixed to obtain a mixed dry material; Adding part of the water to the mixed dry material and stirring, then increasing the stirring speed and adding a water reducing agent and the remaining water, and mixing to obtain a slurry; The slurry is poured into a mold, pre-pressed and allowed to stand, and a sample is obtained after demoulding; 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.

2. A method for preparing a rock-like material containing micron-sized cracks according to claim 1, Features: The silicon dioxide content of the quartz powder is greater than 95%, the particle size is 100 mesh-300 mesh, and the water content is less than 0.1%.

3. The method for preparing a rock-like material containing micron-sized cracks according to claim 1, Features: 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 powder 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.

4. The method for preparing a rock-like material containing micron-sized cracks according to claim 3, Features: The tricalcium silicate content of the 52.5R white silicate cement is greater than 60%.

5. The method for preparing a rock-like material containing micron-sized cracks according to claim 4, Features: The silicon dioxide content of the silicon ash powder is greater than 95%, and the average particle size is less than 50nm.

6. The method for preparing a rock-like material containing micron-sized cracks according to claim 5, Features: The silicon dioxide content of the amorphous nano-silicon dioxide is greater than 99%, and the average particle size is less than 10nm.

7. The method for preparing a rock-like material containing micron-sized cracks according to claim 1, Features: The early strength agent is a solid mixture of sodium aluminate and sodium silicate.

8. The method for preparing a rock-like material containing micron-sized cracks according to claim 1, Features: The water reducing agent is a polycarboxylic acid type liquid water reducing agent, and the water reducing efficiency is greater than 30%.

9. The method for preparing a rock-like material containing micron-sized cracks according to claim 1, Features: 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.

10. A rock-like material containing micron-sized cracks, Features: The rock-like material is prepared by the preparation method described in any one of claims 1 to 9, and contains a micron-scale crack network.

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