CN115340319B - Engineering rock mass heterogeneous simulation test piece based on rock-like resin material, and preparation method and application thereof - Google Patents
Engineering rock mass heterogeneous simulation test piece based on rock-like resin material, and preparation method and application thereof Download PDFInfo
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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B26/00—Compositions of mortars, concrete or artificial stone, containing only organic binders, e.g. polymer or resin concrete
- C04B26/02—Macromolecular compounds
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/20—Mortars, concrete or artificial stone characterised by specific physical values for the density
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
- C04B2201/52—High compression strength concretes, i.e. with a compression strength higher than about 55 N/mm2, e.g. reactive powder concrete [RPC]
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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Abstract
The invention discloses an engineering rock mass non-uniformity simulation test piece and preparation and application thereof, and aims to solve the problem that the existing test piece is difficult to simulate mineral particles so as to cause rock mass non-uniformity. The test piece comprises a rock-like body formed by mixing and casting a transparent resin material and aggregate, and a joint surface buried in the rock-like body. The quartz sand aggregate test piece has good rock-like characteristics at the temperature of minus 15 ℃ to minus 10 ℃ and has the compression strength and tensile strength ratio of 9.12, which is obviously enhanced compared with the test piece before quartz sand is added; the castable is prepared from CY-39 type resin, YS-T31 type curing agent and accelerator according to the proportion of 100:34:4 mass ratio; the quartz sand is transparent particles with the particle size of 0.6-0.8 mm; the joint surface is made of mica sheets. In addition, the material, the shape and the addition amount of the aggregate of the test piece can be changed according to the simulated rock so as to manufacture the same internal structure and mechanical property, the test piece is highly transparent, the internal crack evolution process can be clearly observed, and the method can be effectively used for researching the influence of the size and the shape of the aggregate on the rock mechanism.
Description
Technical Field
The invention relates to the technical field of geotechnical engineering, in particular to an engineering rock mass heterogeneous simulation test piece and a preparation method and application thereof.
Background
Natural rock is a heterogeneous material endowed with a large number of mineral particles, the size and morphology of which have a significant influence on the mechanical and deformation properties of the rock. The problems of instability, damage, shearing bands and other hot spots of rock materials are not separated from the research on the complexity of the rock materials, especially the research on the heterogeneity. Therefore, the method has important academic value and engineering significance for researching the heterogeneous structural characteristics and the destruction mechanism of the rock material. In addition, engineering rock mass generally contains a plurality of macroscopic soft joint surfaces, deformation and strength characteristics of the rock mass are also strongly influenced, and research on the expansion and evolution rules of three-dimensional cracks is also one of key contents of rock mechanics.
The indoor test is an important means for developing geotechnical engineering research, and currently common rock simulation materials comprise cement mortar, ceramic, gypsum, organic glass, photosensitive resin and the like, but the materials have great difficulty in manufacturing heterogeneous simulation test pieces containing aggregate and preset joint cracks in the test pieces, and cannot be consistent with engineering rock mass. In addition, cement mortar, ceramics and gypsum have the disadvantage of being opaque, and no propagation and evolution process of internal cracks is observed; the organic glass has the defects of overlarge difference with rock characteristics and extremely low representativeness; photosensitive resin is a raw material of 3D printing technology, and the shortcoming is to make the test piece through mode printing, solidification layer by layer, consequently leads to the test piece wholeness poor, and photosensitive resin plasticity degree is high, and is poor with rock similarity.
Therefore, how to find a transparent rock-like material, to manufacture heterogeneous pore structure characteristics consistent with the rock structure in the transparent rock-like material, to directly observe the internal damage and crack propagation process by naked eyes, and to preset three-dimensional cracks to develop the indoor experimental study of the engineering rock destabilization mechanism, the transparent rock-like material has important academic value and engineering significance.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide an engineering rock mass heterogeneity simulation test piece and preparation and application thereof, so as to solve the technical problem that the existing rock-like material is difficult to effectively simulate the high brittleness and heterogeneity of real rock.
In order to solve the technical problems, the invention adopts the following technical scheme:
designing a heterogeneous rock-like test piece, wherein the test piece comprises a rock-like body formed by mixing and casting high-brittleness transparent resin and quartz sand and a joint surface buried in the rock-like body; the high brittleness transparent resin consists of CY-39 type resin, YS-T31 type curing agent and dithiodibenzothiazyl curing accelerator according to the weight ratio of 100:34:4 mass ratio; the joint surface is made of transparent mica sheets with corresponding shapes.
For example, fig. 1 (a) is a cross section of the heterogeneous rock-like test piece and fig. 1 (b) is a cross section of a real rock in nature, and it can be seen that both are consistent in the scale and distribution of the fine aggregate/mineral particles, illustrating the effectiveness of the test piece in simulating the internal structure of the real rock.
Transparent particles with the particle size of 0.6-0.8 and mm are different from liquid resin in particle density.
The preparation method of the heterogeneous rock-like test piece comprises the following specific steps:
(1) Preparing a resin casting material: taking CY-39 type resin, YS-T31 type curing agent and dithiodibenzothiazyl curing accelerator according to the weight ratio of 100:34:4, uniformly mixing the materials according to the mass ratio and removing bubbles;
(2) Mixing aggregate: adding quartz sand into the mixture according to 5% of the mass of the mixture obtained in the previous step, placing the mixture on a centrifugal table for 2 minutes after full vibration, and then uniformly stirring the mixture for bubble removal treatment;
(3) Joint surface layout: arranging and fixing joint surfaces required by the test in corresponding test piece casting molds;
(4) Pouring and curing a test piece to form: and (3) draining and pouring the resin castable into a test piece casting mold with the joint surface laid, carrying out bubble removal treatment, carrying out constant temperature maintenance at 20 ℃ for 35 h, demolding, and carrying out constant temperature maintenance at 70-80 ℃ for 48 h. A finished test piece is shown in fig. 2.
The test piece casting mold is an organic polymer silica gel (HTV) mold; as shown in fig. 3.
The joint surface is a round or oval sheet punched by a mica sheet with the thickness of 0.1 and mm, and fig. 4 is a steel mould structure diagram and a physical diagram for processing the mica sheet; a finished mica sheet joint surface is shown in fig. 5.
The transparent quartz sand with the particle size of 0.6-0.8 and mm has long exploring process for the color, performance and shape of aggregate in the early stage, and tens of materials and different particle sizes are tried. Since the particle density of the silica sand is different from that of the liquid resin, precipitation, floating or aggregation and the like are generated (see fig. 6 for a partially failed sample), and the silica sand cannot be effectively distributed in the test piece, resulting in experimental failure. Besides the conventional treatment measures such as vibrating, centrifuging, stirring and the like, the adopted method is to add dithiodibenzothiazyl curing accelerator into the mixture, so as to accelerate the initial setting speed and ensure that the initial setting is completed within 30 min; the disease phenomenon will not occur in the subsequent slow solidification process.
In the step (4), after demolding, drying and curing 24 h at a constant temperature of 70 ℃ to obtain a test piece with the compressive strength of 96.7 MPa.
Compared with the prior art, the invention has the main beneficial technical effects that:
(1) The transparent rock-like resin test piece provided by the invention has important significance for researching the influence mechanism of heterogeneity on the mechanical properties of rock materials.
(2) The transparent rock-like resin test piece prepared based on the brittleness and toughness increase of the aggregate has similar internal structure and mechanical property as the real rock, and has good brittleness and transparency at a lower temperature; the method can effectively simulate the heterogeneity caused by the defects of uneven distribution of mineral particles, pores, joints and the like in the rock; furthermore, transparent quartz sand is selected as aggregate, so that the high transparency of the test piece is not affected, the deformation and crack expansion of the test piece are not affected, the test piece is closer to real rock than a pure resin rock test piece, and the brittleness is obviously improved (9.12); the integrity is stronger than that of the 3D printing photosensitive resin, and the mechanical property is more similar to that of real rock.
(3) The heterogeneous internal structure of the heterogeneous rock-like test piece can be adjusted and changed according to the actual conditions of different engineering rock bodies and the material quality, the addition amount and the body shape parameters of the aggregate, as shown in fig. 7, so as to keep consistent with the structure and the form of the heterogeneous mass of the simulated rock and the elastic modulus.
The aggregate addition amount calculating method comprises the following steps: when the density of the particle defect and the rock main skeleton is the same or less than 10%, firstly obtaining the mass percent information (marked omega) of the fine particles/aggregate in the real rock (cement mortar test piece can also be used) 1 ) The aggregate addition amount in step 2 is ω 2 =138ω 1 /(1-ω 1 ) Thus, the aggregate content omega can be directionally prepared 1 Is a rock-like test piece of (2). In the aspect of aggregate body shape parameters, information such as circularity, sphericity, flatness and the like of particle defects in natural rock is firstly obtained by CT scanning, then a uniform aggregate form and mixing doping amount are processed for manufacturing a test piece, and if necessary, the aggregate can be firmly bonded by glue and then placed in a die for layout. FIG. 8 shows the test pieces produced when different aggregate addition amounts and body shape parameters were selected.
When the density difference between the particle defect and the rock main skeleton is more than 10%, the addition amount of the aggregate is as follows:
wherein:
is the volume ratio of aggregate>
Is the elastic modulus of the resin material +.>
For the modulus of elasticity of the rock to be simulated, +.>
Is boneBody shape parameters of the material->
Poisson's ratio for the resin material.
Wherein,,
as a function of aggregate shape parameters and poisson's ratio of the resin material, the following was calculated:
wherein:
is the minimum value of the tangential angle in the geometric profile of the aggregate.
(4) In the invention, a pouring test piece mold made of silica gel is further selected, and compared with a mold made of glass, stainless steel, polymethyl methacrylate (PMMA), polyvinyl chloride (PVC) and other materials which are conventionally used, bubbles are not easy to adhere to the inner wall of the mold, and as shown in FIG. 9, the mold is a part of samples which are failed to prepare due to the problem of the mold material; the test piece is easier to demould after being molded; the high transparency of the glass fiber reinforced plastic can clearly observe the curing process of a test piece; the method has the advantages that the positions of the joints are positioned by the silica gel soft and convenient drilling and pulling lines, joint surfaces with various conditions are easy to preset, the study on crack expansion of joint sizes, positions, inclination angles and the like is carried out, the influence of the number, relative positions, relative angles and the like of the joint surfaces on crack expansion is carried out, and the study on interaction among the multiple joint surfaces is carried out.
Drawings
FIG. 1 is a cross-sectional comparison of a test piece and a real rock of nature in an embodiment of the present application; wherein a is the test piece of the invention and b is basalt.
Fig. 2 is a view of a finished test piece in an embodiment of the present application, including a test piece without a preformed joint and a test piece with a preformed joint.
Fig. 3 is an organic polymer silica gel (HTV) mold for casting a test piece according to an embodiment of the present application.
FIG. 4 is a steel mold for machining mica sheet joints in accordance with the present invention; wherein a is a structural diagram, and b is a physical diagram.
FIG. 5 is a schematic illustration of an exemplary embodiment of a joint surface made of a transparent mica sheet; wherein a is 12 (minor axis) ×17 mm (major axis) ellipse, b is 15× 15 mm circle, c is 15×20× 20 mm ellipse, and d is 13×20× 20 mm ellipse.
FIG. 6 is a test piece showing a failure of preparation due to improper selection of aggregate during an implementation in an embodiment of the present application; wherein a is sinking caused by overlarge aggregate density, and b is specimen expansion caused by cementing reaction of aggregate and raw materials such as resin.
Fig. 7 is a schematic view of aggregate according to an embodiment of the present application using different body shape parameters.
FIG. 8 is a graph showing the test piece produced according to the embodiment of the present application with different aggregate addition amounts and different body shape parameters; wherein a is blue rubber particles with the particle size of 2 mm, and b is polyethylene plastic particles with the particle size of 1.2 mm.
FIG. 9 is a sample of a failed preparation due to mold material problems in one embodiment of the present application; wherein a is that dense bubbles are formed on the surface of the test piece after the die is demolded, and b is that the die is not resistant to high temperature and is distorted and deformed by heat generated in the curing process of the test piece.
Fig. 10 is a diagram showing a phenomenon of a crack initiation early stage of a built-in single joint test piece according to another embodiment of the present application, wherein a is a front view of the test piece, and b is a side view of the test piece.
FIG. 11 illustrates a later crack initiation event for a built-in single joint test piece according to another embodiment of the present application; where a is a front view of the test piece and b is a side view of the test piece.
Detailed Description
The following examples are given to illustrate the specific embodiments of the present application with reference to the drawings and examples, but the following examples are only intended to illustrate the present application in detail and are not intended to limit the scope of the present invention in any way.
The instruments and devices referred to in the following examples are conventional instruments and devices unless otherwise specified; the related raw materials are all conventional raw materials on the market unless specified; the detection method and the test method are conventional methods unless otherwise specified.
The existence of a large amount of mineral particles, pores, cracks and joints in the rock mass has extremely complex internal structure and has great influence on practical engineering application; and is therefore very important for the study of cracks and the like in rock mass. In order to simulate the heterogeneity of rock and improve the mechanical property of rock-like materials, transparent quartz sand is added on the basis of pure resin materials, a three-dimensional built-in joint surface is preset, and an integral casting is adopted to manufacture a rock-like test piece for indoor experiments. The heterogeneity of the rock is simulated by selecting proper aggregate through experiments, the material quality, the grain diameter, the physicochemical property, the mechanical property and the like of the aggregate are important to consider, and the selection of the material quality and the grain diameter of the aggregate are important difficulties to be solved. The macroscopic cracks in the rock mass are simulated by burying three-dimensional built-in cracks in the mould in advance, and the material selection, cutting and positioning of the prefabricated three-dimensional cracks are the key of successful experiment.
Embodiment one: the preparation method of the transparent rock-like resin material test piece based on the brittleness and toughness increase of aggregate specifically comprises the following steps:
(1) Preparation of resin, curing agent and curing accelerator
1000 g of CY-39 type resin, 340 g of YS-T31 type curing agent and 40 g of dithiodibenzothiazyl curing accelerator are weighed, poured into a stirring barrel, continuously stirred by a glass rod to be fully mixed to form a mixture, the resin on the side wall and the bottom of the container is fully mixed, and then the mixture is placed into a vacuum box for bubble removal treatment.
The CY-39 resin has the advantages of no smell, no harm, good stability, strong binding power, high curing speed, high strength after curing reaction and the like; after the curing agent YS-T31 is added, a cross-linking reaction can be carried out to generate a thermosetting material with a three-dimensional network, the strength is greatly increased, and the mechanical property of the cured test piece is very similar to that of rock. The choice and amount of curing agent is the biggest factor affecting the mechanical properties.
(2) Mixing of aggregate
And (3) adding aggregate accounting for 5% of the mass of the mixture into the mixture subjected to the bubble removal treatment in the step (1), placing the mixture on a centrifugal table for 2 minutes after sufficient vibration, and carrying out bubble removal treatment for 4 minutes after uniform stirring.
For the selection of aggregate materials in rock-like test pieces, a large number of test exploration is carried out, wherein the test exploration comprises the steps of selecting a plurality of materials with uniform particle sizes for exploration, such as polyethylene plastic particles, acrylic solid round beads, PVC injection molding particles, sky blue acrylic microbeads, transparent quartz sand and the like, and the results show that: the density of the transparent quartz sand is similar to that of the mixture, the transparent quartz sand can be uniformly distributed in the mixture after being mixed, the transparent quartz sand can not react with the resin raw material, and the transparency of a test piece is not affected by the transparent quartz sand; when casting a test piece, other selected materials are too light in aggregate mass and easy to aggregate, cannot be uniformly distributed in the resin mixture, and cannot meet the requirement of pore distribution characteristics; too large and too small density can cause uneven distribution of aggregate, so that the aggregate is sunk or floats on the upper part of a test piece, and the requirements on the uniformity and the compactness of the aggregate distribution cannot be met (see figure 9); too deep a color can affect the transparency of the test piece, and the test piece curing process and the crack expansion process are inconvenient to observe.
During the period, the influence of the particle size of the aggregate on the mechanical property of the test piece is further studied, for example, 6 groups of quartz sand with different particle sizes (0.1-0.2 mm, 0.2-0.4 mm, 0.4-0.85 mm, 0.85-2 mm, 2-3.5 mm and 3.5-5 mm) are selected as the aggregate, 6 groups of rock-like test pieces with different particle sizes are prepared, and the influence of the particle sizes of the aggregate on the mechanical property of the test piece is studied by carrying out various mechanical experiments; the results show that: as the particle size increases, the compressive strength of the test piece tends to increase and gradually changes into brittle fracture; and when the aggregate particle size is smaller, the improvement on the mechanical property of the test piece is not obvious, the observation is not facilitated, the cementing degree of the test piece is lower under the condition that the particle size is too large, the pores are increased, the test piece is close to tension fracture, and the quartz sand particle size is determined to be 0.6-0.8 mm to be more suitable. After the particle size of the aggregate is determined, further experiments and analysis are carried out to obtain the result: the aggregate is made into a hollow structure, which is closer to the internal structure of natural rock, and the mechanical property of the aggregate is improved, so that the aggregate meets the requirements on the aggregate structure. The test piece prepared under the condition has high strength, the distribution of aggregate particles on the section of the test piece can be clearly observed, the deformation characteristic of the test piece cannot be influenced, and the mechanical property is relatively similar to that of various rocks.
(3) Embedding of prefabricated joints
Projection points of joint surfaces are determined on two sides of the silica gel mold, holes are drilled, the joint surfaces are positioned by cotton thread traction, the joint surfaces are embedded in the center of a test piece, and an included angle of 45 degrees is formed between each joint and the horizontal surface.
In the embodiment, the prefabricated joint surface is a mica sheet with the thickness of 0.1 and mm, and the mica sheet is used as a layered rock, so that compared with materials such as metal, plastic, resin, stainless steel sheets and the like, the strength and deformation of a test piece are not affected due to low rigidity; the chemical property is stable, and the resin and the curing agent can not react; the ease of positioning is well suited for simulating hollow fractures present in natural rock. The mica sheet is punched by using a custom steel die, and is cut into elliptical prefabricated cracks with fixed sizes. The influence of crack sizes, dip angles, positions and the like on the strength and crack expansion of the test piece can be studied by manufacturing cracks with different sizes; the expansion can be used for researching the influence of the number, the spacing, the relative position, the relative opening degree and the like of multiple cracks on crack expansion and rock mass damage.
The steel die for processing the prefabricated three-dimensional cracks consists of a metal base and an impact column, and the impact column can freely move in the elliptical hole. An elliptic steel mold with three dimensions is manufactured and is used for stamping mica sheets, so that the problem of stress concentration caused by burrs, sharp corners and rough sections in the prior art when the mica sheets are manually cut is solved. The mica sheet cut by the steel die has accurate size and smooth section, and can accurately control the size of the mica sheet and reduce the manual error.
The silica gel mold for preparing the test piece is a square box body with an opening at the upper part, and is sealed by organic insulating silicone grease to form a whole, so that the corresponding size can be customized according to the test requirement. Compared with the prior art, the glass, stainless steel, polymethyl methacrylate (PMMA), polyvinyl chloride (PVC) and other moulds, the silica gel has stable chemical property, the inner wall is not easy to adhere with bubbles, and the silica gel is soft and easy to demould. In addition, the silica gel has high transparency, and the curing process of the test piece can be clearly observed. In addition, the three-dimensional joint surface arranged in the silica gel mold is drilled, the traction fine wire is more convenient to position, holes are drilled at different positions on two sides of the mold, and test pieces with different numbers, different angles and different relative positions can be manufactured.
(4) Pouring of test piece
Placing a silica gel mold with a pre-embedded joint surface on a workbench, and pouring the mixture added with the aggregate in the step (2) into the mold for casting molding by using a glass rod; and (3) after pouring, placing the die into a vacuum box for bubble removal treatment for 25 minutes, and then placing the die into an 18 ℃ constant temperature drying blast box for maintenance for 40 hours, thus the die can be disassembled.
(5) Curing of test pieces
Placing the test piece into a constant-temperature drying air blowing box, setting different curing temperatures and times for curing, wherein the curing temperature is 70 ℃ and the curing time is 24 hours, so that a transparent rock-like resin test piece with the aggregate brittleness and toughness increased and reduced very similar to those of rock is obtained, the brittleness of the transparent rock-like resin test piece reaches 9.12 at the temperature of-15 to-10 ℃, and the mechanical property is much closer to that of the rock than that of a pure resin rock test piece and a 3D printing photosensitive resin test piece prepared by the prior art; compared with cement mortar rock materials, the strength is improved, and the transparency and the visibility are incomparable advantages; the mechanical properties of the material are relatively similar to those of various real rocks. The main mechanical parameters of the resin material of the invention at-15 to-10 ℃ are shown in table 1, and in addition, the experimental temperature of Dyskin and Wong is-50 ℃ and the experimental temperature of Song is-20 ℃.
TABLE 1 comparison of the physical and mechanical parameters of heterogeneous resin test pieces of the invention and other transparent rock-like materials and part of real rock
As can be seen from Table 1, the heterogeneous resin sample of the present invention has mechanical parameters relatively close to those of real rocks, so that the rocks can be simulated to a certain extent, and the test piece obtained by the present invention has the characteristics of high transparency, easy direct observation by naked eyes, etc.
Embodiment two: verification test
The test piece prepared by the invention is easy to prepare and high in repeatability, a group of rock-like test pieces with completely identical built-in cracks are manufactured, various mechanical experiments such as uniaxial compression, brazilian split and the like are carried out on the rock-like test pieces, the rock-like test pieces are respectively loaded into a certain state and unloaded, a photographing record is carried out, and the whole process of expansion and evolution of the built-in cracks can be obtained, such as the phenomenon of the crack development earlier stage obtained by unloading after the test piece is pressurized to 20 MPa in FIG. 10, and the phenomenon of the crack development later stage obtained by unloading after the test piece is pressurized to 90 MPa in FIG. 11. The global stress-strain curve can be obtained by a test piece global compression process.
And pressurizing the resin test piece containing the single-joint rock, observing the crack expansion evolution process, and analyzing the rock destruction rule. The crack expansion evolution of the test piece under the pressurized condition is subjected to an initial stage, then an elastic deformation stage is carried out, wing cracks are initiated at the upper end of the prefabricated joint at the stage, then wing cracks are generated at the upper end and the lower end of the prefabricated crack, and the expansion scales are approximately synchronous. With the increase of pressure, a crack propagation stage is entered, at which time there are 1 and 2 particularly pronounced plaque-shaped cracks, respectively, near both sides of the wrapped wing crack at the upper end of the pre-slit, while the lower end of the pre-slit, immediately adjacent to both sides of the wrapped wing crack, there are 1 relatively smaller plaque-shaped crack, respectively. And finally, entering a crack acceleration and expansion stage, wherein the petal-shaped cracks and the vertical cracks continue to expand along the loading direction, the bearing capacity of the test piece starts to decline, meanwhile, the test piece is heard to emit dense crackles, and the vertical large cracks form macroscopic fracture surfaces to finally split the test piece to present brittle fracture damage.
While the invention has been described in detail with reference to the drawings and embodiments, those skilled in the art will understand that various specific parameters may be changed or equivalents may be substituted for related components, structures and materials thereof without departing from the spirit of the invention, so as to form a plurality of specific embodiments, which are common variations of the invention and will not be described in detail herein.
Claims (2)
1. The preparation method of the heterogeneous rock-like test piece is characterized by comprising the following steps of:
(1) Preparing a resin casting material: taking CY-39 type resin, YS-T31 type curing agent and dithiodibenzothiazyl curing accelerator according to the weight ratio of 100:34:4, uniformly mixing the materials in a mass ratio, and vacuumizing to remove bubbles;
(2) Mixing aggregate: adding aggregate quartz sand with the grain diameter of 0.6-0.8 mm into the mixture according to 5% of the mass of the mixture obtained in the previous step, placing the mixture on a centrifugal table for 2 minutes after full vibration, and then uniformly stirring the mixture for 4 minutes for bubble removal treatment; the addition amount of the quartz sand is calculated according to the following two conditions:
(1) when the density of the particle defect and the rock main skeleton is the same or the difference is less than 10%, firstly acquiring the mass percent information omega of the fine particles in the real rock by a digital image or CT scanning technology 1 The aggregate addition amount in the step (2) is omega 2 =138ω 1 /(1-ω 1 ) The aggregate content omega is directionally prepared 1 Rock-like test pieces of (a);
(2) when the density difference between the particle defect and the rock main skeleton is more than 10%, the addition amount of the aggregate is as follows:
wherein:
is the volume ratio of aggregate>
Is the elastic modulus of the resin material +.>
In order to simulate the modulus of elasticity of the rock,
wherein,,
as a function of aggregate shape parameters and poisson's ratio of the resin material, the following was calculated:
wherein:
is the minimum value of the tangential angle in the geometric outline of the aggregate;
(3) Macrojoint surface layout: the method comprises the steps of arranging and pasting weak joint surfaces required by a fixing test before pouring a mixture in a test piece mould in a perforation and wire drawing mode to form three-dimensional arrangement combinations with different numbers, different angles and different positions so as to adapt to the requirements of various mechanical experiments;
(4) Pouring and curing a test piece to form: draining and pouring the resin castable into a test piece mould with the joint surface laid, maintaining at a constant temperature of 35 h at 20 ℃, demoulding, and maintaining at a constant temperature of 48 h at 70-80 ℃ to finish the test piece manufacturing; the test pieces were placed 24 h in advance in a freezer at-20 ℃ prior to testing.
2. The method for preparing the heterogeneous rock-like test piece according to claim 1, wherein the test piece casting mold in the step (3) is an organic polymer silica gel mold, the mold has strong thermal stability, does not react with casting materials, is convenient to demold, can ensure the size of the test piece to be perfect to the maximum extent, and can be reused.
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| US4090363A (en) * | 1974-12-17 | 1978-05-23 | Heilmann & Littmann, Bau-Aktiengesellschaft | Dam of earth or rock fill having impervious core |
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| CN104327472B (en) * | 2014-10-17 | 2015-10-07 | 河海大学 | A kind of making method of simulation rock propagation of internal cracks transparent material |
| CN104297011B (en) * | 2014-11-06 | 2016-08-24 | 山东大学 | The shaping of cavern and space-location method in high brittle transparent rock-like materials test specimen |
| KR101669917B1 (en) * | 2016-05-24 | 2016-10-27 | 주식회사 에이투 | Concrete Composition for Exhibition Facility and Preparation Methods of Artificial Rock for Exhibition Facility Using Thereof |
| CN112414827B (en) * | 2020-11-05 | 2023-07-07 | 河南理工大学 | Preparation method of heterogeneous anisotropic transparent rock-like material sample |
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| US4090363A (en) * | 1974-12-17 | 1978-05-23 | Heilmann & Littmann, Bau-Aktiengesellschaft | Dam of earth or rock fill having impervious core |
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