CN115340319A - Engineering rock mass heterogeneous simulation test piece based on rock-like resin material and preparation method and application thereof - Google Patents

Abstract

The invention discloses an engineering rock mass heterogeneity simulation test piece and its preparation and application, aiming at solving the rock mass heterogeneity problem caused by the difficulty in simulating mineral particles in the existing test pieces. The test piece includes a rock-like body formed by mixing transparent resin material and aggregate, and a joint surface embedded in the rock-like body. The quartz sand aggregate specimen has good rock-like characteristics at -15 to -10°C, and the ratio of compressive and tensile strength is as high as 9.12, which is significantly stronger than before adding quartz sand; the castable is made of CY-39 type Resin, YS-T31 type curing agent and accelerator are composed in a mass ratio of 100:34:4; the quartz sand is transparent particles with a particle size of 0.6-0.8 mm; the joint surface is made of mica sheets. In addition, the material, shape and addition amount of the aggregate of the specimen can be changed according to the simulated rock to produce the same internal structure and mechanical properties, and the specimen is highly transparent, and the internal crack evolution process can be clearly observed, which can be Effective in the study of the effect of aggregate size and shape on rock mechanisms.

Description

Engineering rock mass heterogeneity simulation specimen based on rock-like resin material and its preparation method Law and Application

technical field

The invention relates to the technical field of geotechnical engineering, in particular to an engineering rock mass heterogeneity simulation test piece and its preparation method and application.

Background technique

Natural rock is a heterogeneous material with a large number of mineral particles. The size and shape of mineral particles have a significant impact on the mechanical and deformation properties of rocks. The solution to hot issues such as instability and failure of rock materials and shear bands is also inseparable from the study of the complexity of rock materials, especially the study of heterogeneity. Therefore, the research on the heterogeneous structure characteristics and failure mechanism of rock materials has important academic value and engineering significance. In addition, there are many macroscopically weak joints in engineering rock mass, which also strongly affect the deformation and strength characteristics of rock mass. The study of the expansion and evolution of three-dimensional cracks is also one of the key contents of rock mechanics.

Indoor testing is an important means to carry out geotechnical engineering research. Currently, commonly used rock simulation materials include cement mortar, ceramics, gypsum, plexiglass, photosensitive resin, etc. In terms of internal preset joints and fissures, there are great difficulties, which cannot be consistent with the engineering rock mass. In addition, the disadvantage of cement mortar, ceramics and gypsum is that it is opaque, and the expansion and evolution process of internal cracks cannot be observed; the disadvantage of plexiglass is that it is too different from the characteristics of rocks, and its representation is extremely low; photosensitive resin is a raw material for 3D printing technology The disadvantage is that the test piece is made by printing and curing layer by layer, which leads to poor integrity of the test piece, and the photosensitive resin has high plasticity and poor similarity to rocks.

Therefore, how to find a transparent rock-like material, create heterogeneous pore structure characteristics consistent with the rock structure inside, directly observe the internal damage and crack propagation process with the naked eye, and pre-set three-dimensional cracks to carry out engineering rock mass failure. The indoor experimental research on the stability mechanism will have important academic value and engineering significance.

The information disclosed in this background section is only intended to enhance the understanding of the general background of the present invention, and should not be considered as an acknowledgment or any form of suggestion that the information constitutes the prior art that is known to those skilled in the art.

Contents of the invention

The purpose of the present invention is to provide an engineering rock mass heterogeneity simulation test piece and its preparation and application, so as to solve the technical problem that existing rock-like materials are difficult to effectively simulate the high brittleness and heterogeneity of real rock.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

Design a heterogeneous rock-like specimen, including a rock-like body formed by mixed casting of high-brittle transparent resin and quartz sand, and a joint surface embedded in the rock-like body; the high-brittle transparent resin is composed of CY-39 type Resin, YS-T31 type curing agent, and dithiodibenzothiazole curing accelerator are composed in a mass ratio of 100:34:4; the joint surface is made of transparent mica sheets of corresponding shapes.

For example, Fig. 1(a) is the cross-section of the heterogeneous rock specimen, and Fig. 1(b) is the cross-section of real rock in nature. are consistent, indicating the effectiveness of the specimen in simulating the internal structure of real rocks.

The quartz sand is a transparent particle with a particle diameter of 0.6-0.8 mm, and the particle density is different from that of the liquid resin.

Design a method for preparing a heterogeneous rock-like specimen, including the following specific steps:

(1) Preparation of resin castable: Take CY-39 resin, YS-T31 curing agent and dithiodibenzothiazole curing accelerator, mix them evenly at a mass ratio of 100:34:4 and remove air bubbles;

(2) Aggregate mixing: Add quartz sand to it according to 5% of the mass of the mixture obtained in the previous step, place it on a centrifuge table for 2 minutes after the vibration is sufficient, and then perform air removal after stirring evenly;

(3) Joint surface layout: Arrange and fix the joint surface required for the test in the corresponding specimen casting mold;

(4) Specimen casting and curing molding: Drainage and pouring the resin castable into the casting mold of the test piece after the joint surface layout is completed, and after removing air bubbles, it is cured at 20°C for 35 hours and then removed from the mold. Then maintain at a constant temperature of 70-80°C for 48 hours. Figure 2 shows a finished sample.

The casting mold of the test piece is an organopolymer silicone (HTV) mold; as shown in FIG. 3 .

Described joint surface is the circular or elliptical sheet that is stamped by thick 0.1 mm mica sheet, and Fig. 4 is the steel mold structural diagram and physical figure that are used to process mica sheet; As shown in Fig. 5, it is a finished mica Slice joint surface.

The quartz sand is transparent quartz sand with a particle size of 0.6-0.8 mm. In the early stage, a long process of exploration was carried out on the color, performance and shape of the aggregate, and dozens of materials and different particle sizes were tried. Because the particle density of quartz sand is different from that of liquid resin, it will cause precipitation, floating or aggregation (see some failure samples in Figure 6), which cannot be effectively distributed in the test piece, resulting in the failure of the experiment. In addition to conventional vibrating, centrifuging, stirring and other disposal measures, the method adopted is to add dithiodibenzothiazole curing accelerator to the mixture to speed up the initial setting speed and ensure that the initial setting is completed within 30 minutes; During the slow solidification process, the above-mentioned disease phenomena will no longer occur.

In the step (4), after demoulding, dry and cure at a constant temperature of 70°C for 24 hours, and a specimen with a compressive strength of 96.7MPa can be obtained.

Compared with the prior art, the main beneficial technical effects of the present invention are:

(1) The transparent rock-like resin specimen of the present invention is of great significance for studying the mechanism of heterogeneity affecting the mechanical properties of rock materials.

(2) The transparent rock-like resin specimen prepared by the present invention based on aggregate brittleness and toughness reduction has similar internal structure and mechanical properties to real rocks, and has good brittleness and transparency at relatively low temperatures; it can effectively The simulated rock has heterogeneity caused by uneven distribution of mineral particles, pores, joints and other defects; and the further selection of transparent quartz sand as aggregate does not affect the high transparency of the specimen, nor does it affect the deformation and deformation of the specimen. The expansion of cracks is closer to real rocks than pure resin rock specimens, and the brittleness has also been significantly improved (up to 9.12); compared with 3D printed photosensitive resins, the integrity is stronger, and the mechanical properties are closer to real rocks.

(3) The heterogeneous internal structure of the heterogeneous rock specimen can be adjusted and changed according to the actual conditions of different engineering rock masses, the aggregate material, addition amount and shape parameters, as shown in Figure 7, To be consistent with the heterogeneous structure and shape of the simulated rock, as well as the elastic modulus.

The calculation method of the amount of aggregate added is as follows: when the density of particle defects and the main rock skeleton is the same or the difference is within 10%, first obtain the mesoscopic particle/aggregate mass percentage information ( denoted as ω ₁ ), then the amount of aggregate added in step 2 is ω ₂ =138ω ₁ /(1-ω ₁ ), so that a rock-like specimen with aggregate content of ω ₁ can be oriented. In terms of aggregate shape parameters, first use CT scanning to obtain information such as circularity, sphericity, and flatness of particle defects inside natural rocks, and then process consistent aggregate shapes and mixing volumes to make test pieces. The aggregate is firmly bonded with glue and then put into the mold for layout. Figure 8 shows the completed specimens with different aggregate additions and shape parameters.

When the difference between particle defects and the density of the main rock skeleton is greater than 10%, the amount of aggregate added is:

(1)，

(1),

Where: is the volume ratio content of the aggregate, is the elastic modulus of the resin material, is the elastic modulus of the simulated rock, is the shape parameter of the aggregate, and is the Poisson's ratio of the resin material.

Among them, is the function of the shape parameter of the aggregate and the Poisson's ratio of the resin material, calculated as follows:

(2)；

(2);

Where: is the minimum value of the tangent angle in the aggregate geometry profile.

(4) In the present invention, the pouring test piece mold made of silica gel is further selected to be improved. Its inner wall is not easy to attach air bubbles, as shown in Figure 9, which is a part of the sample that failed due to mold material problems; it is easier to demould after the specimen is molded; it has high transparency, and can clearly observe the shape of the specimen. Curing process; the silicone is soft and convenient for drilling and pulling wires to locate the joint position, and it is easy to preset joint surfaces in various situations, and carry out research on crack expansion such as joint size, position, inclination angle, etc., the number, relative position, and relative angle of multiple joint surfaces, etc. The influence on crack propagation, and the interaction between multi-joint surfaces, etc.

Description of drawings

Fig. 1 is a cross-sectional comparison diagram of a test piece in an embodiment of the present application and a real rock in nature; wherein a is the test piece of the present invention, and b is basalt.

Fig. 2 shows the completed test pieces in one embodiment of the present application, including test pieces without prefabricated joints and prefabricated joints.

Fig. 3 is an organopolymer silicone (HTV) mold for pouring a test piece in an embodiment of the present application.

Fig. 4 is the steel mold used for processing mica sheet joints in the present invention; wherein a is a structural diagram, and b is a physical diagram.

Figure 5 is a joint surface made of transparent mica sheets prepared in an embodiment of the present application; where a is 12 (short axis) × 17 mm (major axis) ellipse, b is φ15 mm round, and c is 15 ×20 mm oval, d is 13×20 mm oval.

Figure 6 is a test piece that failed due to improper selection of aggregates in the implementation process of an embodiment of the present application; among them, a is the sinking of the bottom due to excessive aggregate density, and b is the result of cementation reactions between aggregates and resins and other raw materials The specimen expands.

Fig. 7 is a schematic diagram of different shape parameters of aggregates in an embodiment of the present application.

Fig. 8 shows the completed test pieces with different aggregate additions and body shape parameters in an embodiment of the present application; where a is blue rubber particles with a particle size of 2 mm, and b is polyethylene plastic particles with a particle size of 1.2 mm.

Figure 9 is a test piece that failed to be prepared due to mold material problems in an embodiment of the present application; where, a is the formation of dense air bubbles on the surface of the test piece after the mold is demoulded, and b is the formation of dense air bubbles on the surface of the test piece due to the inability of the mold to withstand high temperatures. distorted by heat.

Fig. 10 shows the early stage of crack development of the built-in single-joint test piece in another embodiment of the present application, where a is the front view of the test piece, and b is the side view of the test piece.

Fig. 11 is the phenomenon of the later stage of crack development of the built-in single-joint test piece in another embodiment of the present application; where a is the front view of the test piece, and b is the side view of the test piece.

Detailed ways

The specific implementation of the present application will be described below in conjunction with the accompanying drawings and examples, but the following examples are only used to describe the present application in detail, and do not limit the scope of the present invention in any way.

The instruments and equipment involved in the following examples are conventional instruments and equipment unless otherwise specified; the raw materials involved are commercially available conventional raw materials unless otherwise specified; the detection methods and test methods involved are all conventional if not specified are conventional methods.

The existence of a large number of mineral particles, pores, cracks and joints in the rock mass has an extremely complex internal structure, and has a great impact on practical engineering applications; therefore, it is very important for the study of cracks in rock mass. In order to simulate the heterogeneity of rocks and improve the mechanical properties of rock-like materials, on the basis of pure resin materials, transparent quartz sand is added, three-dimensional built-in joint surfaces are preset, and rock-like specimens are made by integral casting for indoor experiments. To simulate the heterogeneity of rock by selecting suitable aggregates through experiments, the material, particle size, physical and chemical properties, and mechanical properties of aggregates need to be considered emphatically. difficulty. The macroscopic cracks inside the rock mass are simulated by pre-burying the three-dimensional built-in cracks in the mold. The material selection, cutting and positioning of the prefabricated three-dimensional cracks are the key to the success of the experiment.

Embodiment 1: A method for preparing a transparent rock-like resin material specimen based on aggregate brittleness and toughness reduction, which specifically includes the following steps:

(1) Preparation of resin, curing agent and curing accelerator

Weigh 1000 g of CY-39 type resin, 340 g of YS-T31 type curing agent, and 40 g of dithiodibenzothiazole curing accelerator, pour them into the mixing bucket, stir continuously with a glass rod to fully mix to form The mixture, the resin on the side wall and bottom of the container should also be fully mixed, and then placed in a vacuum box for debubbling.

The selected CY-39 type resin has the advantages of odorless and harmless, good stability, strong adhesion, fast curing speed, and high strength after curing reaction; after adding curing agent YS-T31, a crosslinking reaction will occur, forming a three-dimensional network The strength of the thermosetting material is greatly increased, and the mechanical properties of the cured specimen are very similar to those of the rock. The choice and amount of curing agent is the biggest factor affecting its mechanical properties.

(2) Mixing of aggregates

Add aggregates accounting for 5% of the mass of the mixture to the mixture after step (1) degassing treatment, place it on a centrifuge table for 2 minutes after sufficient vibration, and then perform 4 minutes of degassing treatment after stirring evenly.

For the selection of aggregate materials in rock-like specimens, a large number of experimental explorations have been carried out, including the selection of various materials with uniform particle sizes, such as polyethylene plastic particles, acrylic solid beads, PVC injection particles, sky blue Acrylic microbeads, blue acrylic microbeads, transparent quartz sand, etc. The results show that the density of transparent quartz sand is similar to that of the mixture. The transparency of the piece; while other selected materials are too light to aggregate easily when casting the test piece, and cannot be evenly distributed in the resin mixture, which cannot meet the requirements of the pore distribution characteristics; too large or too small density will make the bone The uneven distribution of aggregates leads to sinking or floating on the upper part of the specimen, which cannot meet the requirements for the uniformity and compactness of aggregate distribution (see Figure 9); if the color is too dark, it will affect the transparency of the specimen, making it inconvenient to observe the specimen solidification process and crack propagation process.

During this period, the effect of aggregate particle size on the mechanical properties of the specimen was further studied. For example, six groups of different particle sizes (0.1-0.2 mm, 0.2-0.4 mm, 0.4-0.85 mm, ～3.5 mm, 3.5～5 mm) quartz sand was used as aggregate, and 6 groups of rock-like specimens with different particle sizes were prepared, and a variety of mechanical experiments were carried out on them to study the influence of aggregate particle size on the mechanical properties of the specimens; The results show that: with the increase of the particle size, the compressive strength of the specimen shows an increasing trend, and gradually transforms into brittle failure; and when the aggregate particle size is small, the mechanical properties of the specimen are not significantly improved, and it is not conducive to observation. When the particle size is too large, the degree of cementation of the specimen is low, the pores increase, and the sample is close to tensile failure. It is determined that the particle size of quartz sand is 0.6-0.8 mm. After determining the particle size of the aggregate, after further experiments and analysis, the results are obtained: the aggregate is made into a hollow structure, which is closer to the internal structure of natural rock, and its mechanical properties are improved, which is more in line with the requirements for the aggregate structure. In this case, the strength of the prepared specimen is high, and the distribution of aggregate particles in the cross-section of the specimen can be clearly observed without affecting the deformation characteristics of the specimen, and the mechanical properties are close to those of various rocks.

(3) Embedding of prefabricated joints

Determine the projection point of the joint surface on both sides of the silicone mold, drill holes, and use cotton thread to pull to realize the positioning of the joint surface. In this example, the joint surface is pre-embedded at the center of the test piece, and the angle between the joint and the horizontal plane is set to be 45°.

In this example, the prefabricated joint surface uses a mica sheet with a thickness of 0.1 mm. The mica sheet itself is a layered rock. Compared with metal, plastic, resin, stainless steel sheets and other materials, its low stiffness will not affect the strength and Deformation; stable chemical properties, will not react with resins and curing agents; easy to locate, very suitable for simulating hollow cracks existing in natural rocks. The mica sheet is stamped using a custom steel die and cut into oval prefabricated slits of fixed dimensions. Cracks of different sizes can be made to study the effects of crack size, inclination, position, etc. on the strength of the specimen and crack expansion; expansion can be used to study the number, spacing, relative position, and relative opening of multiple cracks. The influence of crack expansion and rock mass damage.

The steel mold for processing and prefabricating three-dimensional cracks is composed of a metal base and an impact column, and the impact column can move freely in the oval hole. Three sizes of elliptical steel molds were made to stamp mica sheets, which solved the problem of stress concentration caused by burrs, sharp corners, and rough cross-sections in the past when cutting mica sheets by hand. The size of the mica sheet cut by the steel mold is accurate, and the cross section is smooth, which can accurately control the size of the mica sheet and reduce manual errors.

The above-mentioned silicone mold for preparing the test piece is a square box with an upper opening, and is sealed with organic insulating silicone grease to form a whole, and the corresponding size can be customized according to the test requirements. Compared with glass, stainless steel, polymethyl methacrylate (PMMA), polyvinyl chloride (PVC) and other molds used by the predecessors, the chemical properties of silicone are stable, the inner wall is not easy to attach air bubbles, and it is soft and easy to demould. In addition, the silica gel has high transparency, and the curing process of the specimen can be clearly observed. In addition, the built-in three-dimensional joint surface of the silicone mold is drilled, and it is more convenient to pull the thin wire for positioning. Drilling holes at different positions on both sides of the mold can make test pieces with different numbers, different angles, and different relative positions.

(4) Pouring of test pieces

Place the silicone mold with pre-embedded joint surface on the workbench, and pour the mixture added with aggregate in step (2) into the mold with a glass rod for casting; after pouring, put the mold in a vacuum box for 25 minutes to remove air bubbles. Then put it into a 18°C constant temperature drying blower box for curing for 40 hours, and then the mold can be removed.

(5) Maintenance of specimens

Afterwards, put the specimen into the constant temperature drying blower box, and set different curing temperatures and times for curing. In this example, the curing temperature is set at 70°C, and the curing time is 24 hours. The brittleness and toughness of aggregates that are very similar to those of rock brittleness are obtained. The transparent rock resin specimen has a brittleness of 9.12 at -15 to -10°C, which is greatly improved compared with the pure resin rock specimens and 3D printed photosensitive resin specimens prepared before. The rock is closer; compared with the cement mortar rock material, the strength has been improved, and the transparency and visibility are incomparable advantages; the mechanical properties of a variety of real rocks are closer. The main mechanical parameters of the resin material of the present invention at -15 to -10°C are shown in Table 1. In addition, the experimental temperature of Dyskin and Wong is -50°C, and the experimental temperature of Song is -20°C.

Table 1 Comparison of physical and mechanical parameters between the heterogeneous resin specimen of the present invention and other transparent rock-like materials and some real rocks

。

.

As can be seen from Table 1, the heterogeneous resin sample of the present invention is relatively close to the mechanical parameters of real rocks, so these rocks can be simulated to a certain extent, and the obtained test piece of the present invention has high transparency and is easy to be directly seen by naked eyes. Observation and other characteristics.

Embodiment two: Verification test

The test piece prepared by the present invention is easy to prepare and has strong repeatability. By making a group of rock-like test pieces with identical built-in cracks, various mechanical experiments are carried out on them, such as uniaxial compression, Brazilian splitting, etc., and their respective After loading to a certain state, unload and take pictures to record, the whole process of the built-in crack expansion and evolution can be obtained. Figure 10 shows the phenomenon in the early stage of crack development obtained by unloading after pressurizing to 20 MPa, and Figure 11 shows the unloading after pressurizing to 90 MPa The resulting phenomenon of the later stages of crack development. The whole stress-strain curve can be obtained from the whole compression process of a specimen.

Pressurize the rock resin specimen containing single joints, observe the crack expansion and evolution process, and analyze the rock failure law. Under the condition of pressure, the crack propagation evolution of the specimen went through the initial stage, and then entered the elastic deformation stage. In this stage, wing cracks were initiated at the upper end of the prefabricated joints. Subsequently, wing cracks were generated at the upper and lower ends of the prefabricated cracks, and the expansion scales were approximately synchronous. As the pressure increases, it enters the stage of crack propagation. At this time, near the two sides of the wrapped wing crack at the upper end of the prefabricated crack, there are 1 and 2 particularly obvious mottled cracks respectively, while the lower end of the prefabricated crack, and the wrapped wing crack The two sides of the wing cracks are adjacent to each other, and each has a relatively small piebald crack. Finally, it enters the stage of accelerated crack growth, petal-shaped cracks and vertical cracks continue to expand along the loading direction, and the bearing capacity of the specimen begins to decline. At the same time, dense crackling sounds are heard from the specimen. The specimen was split open, showing brittle splitting failure.

The present invention has been described in detail above in conjunction with the accompanying drawings and embodiments. However, those skilled in the art can understand that without departing from the concept of the present invention, the specific parameters in the above embodiments can also be changed. Alternatively, relevant components, structures, and materials are equivalently substituted to form multiple specific embodiments, all of which are common variation scopes of the present invention, and will not be described in detail here.

Claims (5)

1. A heterogeneous rock-like test piece is characterized in that the test piece is highly transparent, can clearly observe the whole-course evolution law of internal cracks and damages by naked eyes, and is applied to the simulation experiment research of various engineering rock masses; the method is realized by adding quantitative aggregate into a transparent resin material to prepare an engineering rock mass simulation test piece with heterogeneous characteristics; taking a quartz sand aggregate test piece as an example, the test piece specifically comprises a quasi-rock body formed by mixing and pouring brittle transparent resin and quartz sand, and a macroscopic soft joint surface embedded in the quasi-rock body; by means of the effects of increasing brittleness and reducing toughness of the aggregate, the rock-like property of the test piece is obviously enhanced compared with that of a homogeneous pure resin test piece without the aggregate, the brittleness, namely the ratio of the compressive strength to the tensile strength, is greatly improved from 6.6 to 9.12, and compared with 2.98 of the prior transparent rock-like test piece of the same type, the brittleness reaches the standard of a plurality of real rocks in the nature.

2. The heterogeneous rock test piece of claim 1, wherein the heterogeneity of the engineering rock is due to the fact that a large number of microscopic particle defects exist inside the engineering rock, and the simulation implementation method is to use transparent quartz sand and the like as pouring aggregates of the pure resin test piece;

because the particle density of the quartz sand is different from that of the liquid resin, the phenomena of precipitation, floating or aggregation and the like can be generated, and the quartz sand cannot be effectively distributed in a test piece, so that the experiment fails; in addition to the measures of conventional vibration, centrifugation, repeated stirring and the like, the dithiodibenzothiazyl curing accelerator is added into the mixture to accelerate the initial setting speed and ensure that the initial setting is completed within 30 min; in the subsequent slow solidification process, the phenomenon of uneven distribution can not occur any more;

the addition amount of the curing accelerator is 4% of the mass of the liquid resin, too much of the curing accelerator influences the mechanical parameters of a cured test piece, and too little of the curing accelerator does not achieve the effect of accelerating initial curing;

in addition, the test piece used for the rock mechanical test needs to contain a macroscopic soft joint surface consistent with real rock except homogeneity so as to meet the requirements of various mechanical tests; the transparent mica sheet is adopted to simulate a joint surface, the thickness of the transparent mica sheet is 0.1 mm, the transparent mica sheet is punched by a steel die to form round and oval sheets, and the edges of the round and oval sheets are neat so as to avoid stress concentration caused by burrs and size defects.

3. The preparation method of the heterogeneous rock-like test piece is characterized by comprising the following steps:

(1) Preparing a resin casting material: taking CY-39 type resin, YS-T31 type curing agent and dithiodibenzothiazole curing accelerator, and mixing the components in a proportion of 100:34:4, uniformly mixing, and vacuumizing to remove bubbles;

(2) Mixing aggregate: adding the quartz sand of claim 2 into the mixture according to 5 percent of the mass of the mixture obtained in the previous step, placing the mixture on a centrifugal table for processing for 2 minutes after fully vibrating, and then carrying out bubble removal processing for 4 minutes after uniformly stirring;

(3) Laying a macroscopic joint surface: the method is characterized in that a perforation and line drawing mode is adopted in a test piece die, soft joint surfaces required by a fixed test are arranged and stuck before a mixture is poured, and three-dimensional arrangement combinations with different numbers, different angles and different positions are formed so as to meet the requirements of various mechanical experiments;

(4) Pouring and curing the test piece: pouring the resin casting material into a test piece mold with the joint surfaces arranged, maintaining at the constant temperature of 20 ℃ for 35 h, then demolding, and maintaining at the constant temperature of 70-80 ℃ for 48 h to finish the manufacture of the test piece; before the test, the test piece was placed in a freezer at-20 ℃ in advance at 24 h.

4. The heterogeneous rock-like test piece of claim 3, wherein in the step (2), the material, form and addition amount of the aggregate are variable, and the form of the aggregate is consistent with the form of the particle defect in the natural rock, and the addition amount of the aggregate is calculated according to the following two conditions in order to make the macroscopic elastic modulus of the test piece consistent with the simulated rock:

(1) when the density of the particle defect is the same as or within 10 percent of that of the main skeleton of the rock, acquiring the mass percent information omega of microscopic particles in the real rock by a digital image or CT scanning technology ₁ If the amount of the aggregate added in the step (2) is ω ₂ =138ω ₁ /(1-ω ₁ ) The aggregate content omega is prepared by the orientation ₁ The rock-like test piece of (1);

(2) when the density difference between the particle defects and the rock main body skeleton is more than 10%, the addition amount of the aggregate is as follows:

(1)；

in the formula: the volume ratio content of the aggregate, the elastic modulus of the resin material, the elastic modulus of the simulated rock, the body shape parameter of the aggregate and the Poisson ratio of the resin material are shown;

wherein, as a function of the aggregate shape parameter and the poisson's ratio of the resin material, the following is calculated:

(2)；

in the formula: is the minimum value of the tangent angle in the geometric profile of the aggregate.

5. The method for preparing the heterogeneous rock-like test piece according to claim 3, wherein the test piece casting mold in the step (3) is an organic polymer silica gel mold which has strong thermal stability, does not react with the casting material, is convenient to demold, can ensure the test piece to be intact to the maximum extent, and can be reused.

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