Method and system for preparing fractured composite rock

Abstract

The invention belongs to the technical field of rock mass performance research, and discloses a method for preparing composite rock with fractures, which comprises the following steps: transforming a cubic ABS (acrylonitrile butadiene styrene) plastic mold, and marking a groove in the center inside the mold for placing a steel plate; for a rock sample with a crack located in the middle of a similar rock, different crack inclination angles, lengths and positions are drawn through Microsoft Visio drawing software, the crack inclination angles, lengths and positions are printed, sheared and pasted to the surface of a mold to determine the positions of the cracks, thin steel sheets heated at high temperature are used for scalding and melting at specific positions of the two sides of the mold, and a reserved opening is obtained, and the steel sheets can be placed in advance before slurry is poured. The rock sample preparation process comprises the steps of mold preparation, slurry preparation, pouring and vibrating, mold removal and maintenance, core drilling and sampling, end cutting and sample polishing. The method for manufacturing the fissure-containing composite rock cylindrical standard test piece for the indoor triaxial test is convenient to operate, high in practicability and accurate in fissure positioning, and can be generally used for preparing fissure-containing composite rock samples.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock mass performance research, and particularly relates to a method and system for preparing a fractured composite rock. Background Art

[0002] Layered composite rocks are commonly found in the field of underground engineering and are formed by the layered accumulation of two or more rocks with different lithologies. There are often various defects inside them, and their special structural form is one of the important factors leading to their instability and deformation. Many scholars have studied the mechanical properties and failure modes of fractured rocks by means of indoor experiments or numerical simulations, but mostly they used on-site sampling. In the natural state, the rock contains defects such as fractures, joints and holes of different scales. Coupled with the possible damage to the rock samples caused by sampling, processing and transportation, these defect damages affect and even dominate the mechanical properties of the rock. Therefore, finding a method that can freely control the fracture configuration and lithology composition can effectively reduce errors, prepare a large number of samples for experiments, and explore the general laws of the mechanical properties of fractured rocks. Rock mechanics experiments need to control variables, and the existing rock sample production methods are difficult to ensure the isotropy of the rock samples. The current research status of the production methods for fractured rock masses is as follows:

[0003] The patent "A Mold for Making a Rock-Like Specimen with Non-Penetrating Fractures" introduces a mold for making a rock-like specimen with non-penetrating fractures. (See patent application number CN201610517486.5). This method uses a combined mold to produce specimens with non-penetrating fractures and cannot produce penetrating fractures.

[0004] The patent "A Device and Method for Preparing Pre-Fractures of Standard Rock Specimens" introduces a device and method for preparing pre-fractures of standard rock specimens. The device mainly consists of a cutting system, a driving system and a table system. (See patent application number CN201810966289.0). This method uses mechanical cutting, which will damage the rock sample and affect the mechanical properties.

[0005] The patent "A Device for Making Surface Fractures of Standard Rock Specimens" introduces a device for making surface fractures of standard rock specimens. (See patent application number CN201720749290.9). This device cannot realize the production of penetrating fractures and has great limitations on the size of the fractures. It cannot produce penetrating fractures.

[0006] The patent "A Device for Making Penetrating Fractures of Standard Rock Specimens without Damage" introduces a device for making penetrating fractures of standard rock specimens without damage. The device mainly consists of a motor, a diamond saw, a steel rail, a fixture and a bracket. (See patent application number CN201621371975.6). This method has a complex composition, high use cost, and can only produce one specimen at a time.

[0007] The patent "Preparation Method of Rock Specimens with Damage Fracture System" introduces a preparation method of rock specimens with damage fracture system. This method cuts an existing rock sample to obtain a standard specimen and conducts a uniaxial compression test to make a fractured specimen. (See patent application number CN201410565876.0). The occurrence of the fractures produced by this method is uncontrollable.

[0008] Through the above analysis, the problems and defects of the existing technology are as follows:

[0009] (1) For the patent "A Mold for Making Rock-Like Specimens with Non-Penetrating Fractures", this method uses a combined mold to make non-penetrating fractures and cannot make penetrating fractures.

[0010] (2) For the patent "A Device and Method for Preparing Pre-Fractures of Standard Rock Specimens", this method uses mechanical cutting, which will cause damage to the rock sample and affect its mechanical properties.

[0011] (3) For the patent "A Device for Making Surface Fractures of Standard Rock Specimens", this device cannot achieve the production of penetrating fractures and has great limitations on the size of the fractures. It cannot make penetrating fractures.

[0012] (4) For the patent "A Device for Making Non-Destructive Penetrating Fractures of Standard Rock Specimens", this method has a complex composition, high use cost, and can only make one specimen at a time.

[0013] (5) For the patent "Preparation Method of Rock Specimens with Damage Fracture System", this method uniaxially compresses a complete rock sample, and the occurrence of the fractures produced is uncontrollable, with low production efficiency and high cost. Summary of the Invention

[0014] In view of the problems existing in the prior art, the present invention provides a preparation method of composite rock with fractures.

[0015] The present invention is implemented as follows. A preparation method of composite rock with fractures includes:

[0016] Step 1: Modify a 150mm×150mm×150mm cubic plastic mold, draw a groove at the central position inside the mold, and place a 180mm×155mm×1mm high-strength steel plate as a detachable partition to obtain a mold 1 for forming a rock-like composite sample.

[0017] Step 2: Use Microsoft Visio drawing software to draw fracture parameter diagrams with different fracture dips, lengths, and positions, print them at a 1:1 ratio and paste them on the outer surface of the mold in position. Use a heated steel sheet to perform double-sided synchronous melting at specific fracture positions to form a prefabricated fracture channel, and insert a thin steel sheet to obtain a mold 2 with fractures in the middle of the rock-like sample.

[0018] Step 3: Prepare a crack positioning base by wire cutting a high-strength steel plate, and assemble it with a solid nylon buckle with a height of 15 mm and a diameter of 30 mm and a steel sheet with sandblasted surface to form a crack positioning device;

[0019] Step 4: Apply release oil evenly on the inner surfaces of mold 1 and mold 2, prepare the slurry according to the rock-like mix ratio, fill the slurry into the molds respectively, and place them on a vibrating table for 15 seconds of oscillation;

[0020] Step 5: After oscillation, let it stand for 30 minutes, draw out the partition in mold 2 to obtain a cubic specimen with a crack in the middle of the rock-like material; slowly insert the steel sheet of the crack positioning device into mold 1 according to the position of the steel plate and the mold to obtain a cubic specimen with a crack at the interface;

[0021] Step 6: 24 hours after pouring, use an air pump to blow air at the bottom of the mold for demolding, cure for 28 days, take cores by a core drill, cut the ends, and polish to obtain a standard cylindrical rock sample with a crack of Φ×h = 50 mm×100 mm.

[0022] Further, in step 1, the depth of the grooves at the bottom and on the side is 3 mm, and the width is 1.0±0.2 mm.

[0023] Further, in step 2, in the dimensions of the steel sheet, L is the crack length, the length is 180 mm, and the thickness is 1.0±0.2 mm.

[0024] Further, in step 3, the length of the guiding slot of the crack positioning base is equal to the crack length L, the angle is equal to the crack inclination angle α, and the width is 1.0±0.2 mm;

[0025] In step 3, the steel sheet penetrates through the nylon buckle and the steel sheet. The nylon buckle is located on one side of the steel sheet, and the length of the other side of the steel sheet is 155 mm;

[0026] In step 4, in the dimensions of the steel sheet, L is the crack length, the length is 180 mm, and the thickness is 1 mm.

[0027] Further, in step 5, the steel sheet is pulled out and the crack positioning device is taken out within 10 hours after pouring.

[0028] Further, in step 6, during the cutting process, the length of both types of rock-like samples is 50 mm, and the total length is 100 mm.

[0029] Another object of the present invention is to provide a preparation system for cracked composite rock, including:

[0030] Reform module, used to reform a 150mm×150mm×150mm cubic plastic mold, draw a groove at the central position inside the mold, and place a 180mm×155mm×1mm high-strength steel plate as a detachable partition to obtain a mold 1 for forming a composite rock-like sample;

[0031] Drawing module, used to draw crack parameter diagrams with different crack dip angles, lengths and positions using Microsoft Visio drawing software, print them at a 1:1 ratio and paste them on the outer surface of the mold in position. Use a heated steel sheet to perform double-sided synchronous heat fusion at specific crack positions to form a prefabricated crack channel, and insert a thin steel sheet to obtain a mold 2 with cracks in the middle of the rock-like material;

[0032] Cutting module, used to prepare a crack positioning base by wire cutting of high-strength steel plates, cooperate with a solid nylon buckle with a height of 15mm and a diameter of 30mm, and assemble with a steel thin sheet with surface sandblasting treatment to form a crack positioning device;

[0033] Oscillation module, used to evenly coat the inner surfaces of mold 1 and mold 2 with release agent, prepare slurry according to the mix ratio of the rock-like material, fill the slurry into the molds respectively, and place them on a vibrating table for oscillation for 15 seconds;

[0034] Static module, used to stand still for 30 minutes after oscillation, remove the partition in mold 2 to obtain a cubic specimen with cracks in the middle of the rock-like material; slowly insert the steel thin sheet of the crack positioning device into mold 1 according to the position of the steel plate and the mold to obtain a cubic specimen with cracks at the interface;

[0035] Demoulding module, used to blow air to demould the bottom of the mold 24 hours after pouring, cure for 28 days, take cores through a core drill, cut the ends, and polish to obtain a standard cylindrical rock sample with cracks of Φ×h=50mm×100mm.

[0036] Combining the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by the present invention are as follows:

[0037] First, the present invention can prepare similar material specimens of two different lithologies, and the geometric dimensions of the cracks can be freely set, so that a large number of specimens can be obtained for rock mechanics tests accordingly.

[0038] The technical solution adopted by the present invention to solve its technical problems is as follows: A mold for prefabricated specimens with cracks and a preparation method thereof are provided in the present invention. The mold includes a cubic ABS plastic mold, a high-strength steel plate, a steel sheet, and a crack positioning device. The cubic ABS plastic mold is an upper-open cubic mold with demolding air holes at the bottom, and grooves are drawn on the central bottom surface and the side surface inside. A rectangular high-strength steel plate is used as a partition and is embedded in the groove. The position of the crack in the mold is determined through a crack parameter diagram, and double-sided synchronous hot melting is carried out using the steel sheet, and a long strip-shaped steel sheet is embedded. The crack positioning device includes a processed steel sheet crack positioning base, a solid nylon buckle, and a steel sheet. The steel sheet and the nylon buckle are prefabricated with a guiding slit, and the steel sheet penetrates and combines them into one body. The nylon buckle is located on one side of the steel sheet, and the length of the steel sheet reserved on the other side is 155 mm. The preparation method includes: mold preparation, slurry preparation, pouring and vibrating, demolding and curing, core drilling and sampling, end cutting, and specimen grinding.

[0039] The present invention provides a preparation mold and a preparation method for making prefabricated crack-containing composite rock samples. The mold includes a 150 mm × 150 mm × 150 mm cubic ABS plastic mold, a 180 mm × 155 mm × 1 mm high-strength steel plate, an 180 mm × L × 1 mm steel sheet, and a crack positioning device. The preparation steps include: transforming the cubic ABS plastic mold, and drawing a groove at the central position inside the mold for placing the steel plate. For the rock sample with cracks in the middle of the rock-like material, use Microsoft Visio drawing software to draw different crack inclinations, lengths, and positions, print and cut and paste them on the surface of the mold to determine the crack position, and use a thin steel sheet heated by high temperature to perform hot melting at specific positions on both sides of the mold to obtain a reserved opening for placing the steel sheet in advance before pouring the slurry. For the rock sample with cracks at the interface, vibrate after pouring the slurry, let it stand for 30 minutes, pull out the partition after the slurry solidifies, and use crack positioning devices with different crack inclinations and lengths to vertically insert the steel sheet into the mold. The rock sample preparation process is: mold preparation, slurry preparation, pouring and vibrating, demolding and curing, core drilling and sampling, end cutting, and specimen grinding. The method for making crack-containing composite rock cylindrical standard specimens for indoor triaxial tests provided by the present invention is convenient to operate, highly practical, and accurate in crack positioning, and can be generally used for the preparation of crack-containing composite rock samples.

[0040] Second, the expected benefits and commercial value after the transformation of the technical solution of the present invention are as follows: The present invention provides a preparation method for making crack-containing rock-like materials using similar materials, which can make two types of crack-containing composite rock specimens for mechanical tests, effectively reducing the test cost.

[0041] The technical solution of the present invention fills the technical gaps at home and abroad: The present invention fills the technical gap of prefabricated cracked composite rock samples, provides a method for preparing two types and four rock samples at one time, can better control variables and reduce errors caused by uncertain factors.

[0042] Does the technical solution of the present invention solve the technical problems that people have been eager to solve but have never been successful? The present invention solves the problem that it is difficult to prepare when two structural planes intersect during the preparation of composite rock. The present invention can accurately and effectively prefabricate cracks on different lithological structural planes of composite rock. Brief Description of the Drawings

[0043] Figure 1 It is a flow chart of the method for preparing cracked composite rock provided by the embodiment of the present invention.

[0044] Figure 2 It is a structural block diagram of the system for preparing cracked composite rock provided by the embodiment of the present invention.

[0045] Figure 3 It is a diagram of the cylindrical specimen after core drilling and processing provided by the embodiment of the present invention.

[0046] Figure 4 It is a schematic structural diagram of the processed composite rock-like forming mold 1 provided by the embodiment of the present invention.

[0047] Figure 5 It is a schematic structural diagram of the mold 2 with cracks in the middle of the sandstone-like provided by the embodiment of the present invention.

[0048] Figure 6 It is a schematic diagram of the crack positioning device 3 provided by the embodiment of the present invention.

[0049] Figure 7 It is an unfolded schematic diagram of the crack positioning device 3 provided by the embodiment of the present invention.

[0050] Figure 8 It is a cube specimen after demolding provided by the embodiment of the present invention.

[0051] In the figure: 1. Cracked cylindrical rock sample; 2. Plastic mold with chute; 3. High-strength steel plate; 4. Steel sheet; 5. Crack positioning base; 6. Nylon buckle; 7. Cube specimen. Detailed Embodiment

[0052] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0053] Such as Figure 1As shown in the figure, a method for preparing a composite rock with cracks according to an embodiment of the present invention includes the following steps:

[0054] S101: Modify a 150mm×150mm×150mm cubic plastic mold, draw a groove at the central position inside the mold, and place a 180mm×155mm×1mm high-strength steel plate as a detachable partition to obtain a mold 1 for forming a composite rock-like sample;

[0055] S102: Use Microsoft Visio drawing software to draw crack parameter diagrams with different crack inclinations, lengths, and positions, print them at a 1:1 ratio, position and paste them on the outer surface of the mold, and use a heated steel sheet to perform double-sided synchronous melting at specific crack positions to form a prefabricated crack channel, and insert a thin steel sheet to obtain a mold 2 with cracks in the middle of the rock-like material;

[0056] S103: Prepare a crack positioning base by wire cutting the high-strength steel plate, cooperate with a solid nylon buckle with a height of 15mm and a diameter of 30mm (a central prefabricated L×1.2mm guiding slot), and assemble it with a steel sheet with surface sandblasting treatment to form a crack positioning device 3;

[0057] S104: Uniformly apply a release agent on the inner surfaces of mold 1 and mold 2, prepare a slurry according to the mix ratio of the rock-like material, pour the slurry into the molds respectively, and place them on a vibrating table for 15 seconds of vibration;

[0058] S105: After vibration, let it stand for 30 minutes, take out the partition in mold 2 to obtain a cubic specimen 7 with cracks in the middle of the rock-like material; slowly insert the steel sheet of the crack positioning device 3 into mold 1 according to the position of the steel plate and the mold to obtain a cubic specimen 7 with cracks at the interface;

[0059] S106: 24 hours after pouring is completed, use an air pump to blow air at the bottom of the mold for demolding, cure for 28 days, take cores through a core drill, cut the ends, and polish to obtain a standard cylindrical rock sample with cracks of Φ×h = 50mm×100mm.

[0060] In step one provided by the embodiment of the present invention, the depth of the bottom and side grooves is 3mm, and the width is 1.0±0.2mmmm.

[0061] In step two provided by the embodiment of the present invention, in the dimensions of the thin steel sheet, L is the crack length, the length is 180mm, and the thickness is 1.0±0.2mmmm.

[0062] In step three provided by the embodiment of the present invention, the length of the guiding slot of the crack positioning base is equal to the crack length L, the angle is equal to the crack inclination angle α, and the width is 1.0±0.2mm;

[0063] In Step 3, the steel sheet penetrates through the nylon buckle and the steel sheet. The nylon buckle is located on one side of the steel sheet, and the length of the other side of the steel sheet is 155 mm.

[0064] In Step 4, in the dimensions of the steel sheet, L is the crack length, with a length of 180 mm and a thickness of 1 mm.

[0065] In Step 5 provided by the embodiment of the present invention, the steel sheet is pulled out within 10 hours after pouring is completed, and the crack positioning device 3 is taken out.

[0066] In Step 6 provided by the embodiment of the present invention, during the cutting process, the lengths of both types of rock samples are 50 mm, and the total length is 100 mm.

[0067] As Figure 2 shown, a preparation system for a composite rock with cracks provided by the embodiment of the present invention includes:

[0068] As Figure 3 , Figure 4 , a transformation module for transforming a 150 mm × 150 mm × 150 mm cubic plastic mold, marking a groove at the central position inside the mold, and placing a 180 mm × 155 mm × 1 mm high-strength steel plate as a detachable partition to obtain a mold 1 for forming a similar composite rock sample;

[0069] As Figure 5 , a drawing module for using Microsoft Visio drawing software to draw crack parameter diagrams with different crack inclinations, lengths, and positions, printing them at a 1:1 ratio and positioning and pasting them on the outer surface of the mold, using a heated steel sheet to perform bilateral synchronous melting at specific crack positions to form a prefabricated crack channel, and inserting a steel sheet to obtain a mold 2 with a crack located in the middle of the similar rock;

[0070] As Figure 6 , Figure 7 , a cutting module for preparing a crack positioning base by wire cutting of a high-strength steel plate, cooperating with a solid nylon buckle with a height of 15 mm and a diameter of 30 mm (a central prefabricated L × 1.2 mm guiding slot), and assembling with a steel sheet with surface sandblasting treatment to form a crack positioning device 3;

[0071] An oscillation module for evenly coating the inner surfaces of the mold 1 and the mold 2 with release oil, preparing a slurry according to the mix ratio of the similar rock, filling the slurry into the molds respectively, and placing them on a vibrating table for oscillation for 15 seconds;

[0072] A static module for standing for 30 minutes after oscillation, pulling out the partition in the mold 2 to obtain a cubic specimen 7 with a crack located in the middle of the similar rock; slowly inserting the steel sheet of the crack positioning device 3 towards the mold 1 according to the position of the steel plate and the mold to obtain a cubic specimen 7 with a crack located at the interface;

[0073] The demoulding module is used to blow air at the bottom of the mold with an air pump for demoulding 24 hours after pouring is completed, cure for 28 days, take cores with a core drill, cut the ends, and polish to obtain standard cylindrical rock samples with cracks, Φ×h = 50mm×100mm.

[0074] The system implements geometric reconstruction on a standard cubic plastic mold, and presets a U-shaped or rectangular groove area at the center of its inner cavity for embedding high-strength steel plates as partitions. The high-strength steel plates used have high modulus and are reusable. During the forming process, they act as a rigid support structure and ensure the geometric consistency and positioning accuracy of the crack interface. The modified mold is defined as a composite rock-like sample forming mold, which can be used to generate multi-phase material models with interface simulation characteristics to meet the experimental requirements of rock-like heterogeneous structures.

[0075] The crack design is modeled using Visio software. Based on the linear fracture theory and the crack propagation model of anisotropic materials, the dip angle, length, and distribution parameters are set. Through high-precision drawing positioning at a 1:1 ratio, narrow steel sheets (width controlled within 1.2 - 1.5mm) after heating are embedded bilaterally along the crack path in the drawing. The hot melt cutting technology realizes directional melting and breaking of the boundary, and locally carbonizes the inner wall of the plastic mold to form a prefabricated crack channel. This step ensures the positioning accuracy of the subsequent steel sheet insertion process and the simulation stability of the crack geometric boundary.

[0076] Use CNC wire cutting technology to machine positioning grooves with standard geometry on the high-strength steel plate, and mechanically fit them with high-rigidity nylon fasteners. The guiding slot preset in the center of the fastener cooperates with the steel sheet (the surface is sandblasted to improve the interface adhesion and friction coefficient) to form a crack insertion constraint channel, which can control the insertion direction, depth, and dip angle. The crack positioning device cooperates with the edge of the bottom surface of the mold to ensure that the steel sheet can be inserted at the specified interface to form an artificial crack zone.

[0077] According to the mix ratio principle of mortar-like rock-like materials (such as the ash-sand ratio, water-cement ratio, etc.), prepare the slurry, and its workability should meet the slump range of 30 - 50mm. After the mold is filled with the slurry, it is placed on a horizontal triaxial vibration platform and vibrated for 15 seconds to promote the slurry to fill the mold cavity evenly and densely, effectively eliminating pores and reducing the initial defect rate. The inner wall of the mold is coated with demoulding oil to form a temporary isolation film to prevent the hydration products from adhering to the inner wall of the mold in the initial hardening stage and ensure the integrity of demoulding.

[0078] After the initial vibration, let it stand still for 30 minutes to provide a buffer window for the formation of fracture channels and the initial setting stability. Remove the central partition in mold 2 at this stage, insert steel sheets into the preset fracture channels to simulate the middle-embedded fracture mode; for mold 1, insert the steel sheets from the edge through the fracture positioning device to achieve the interface staggered fracture mode. These two fracture layout methods can respectively simulate the through fractures and joint surfaces in natural rock masses, making the composite rock samples have the characteristics of structurally controlled fractures and multiphase interfaces.

[0079] 24 hours after the pouring is completed, use an air pump to blow air under pressure from the bottom of the mold, and cooperate with the conical inner cavity of the mold to achieve smooth demolding. After the samples are cured under standard conditions for 28 days, core drilling is carried out, and standard cylindrical rock samples with a diameter of 50 mm and a length of 100 mm are extracted using diamond drill bits. Subsequently, the end faces are trimmed through an automatic end face grinding device to ensure that the flatness and perpendicularity of the rock samples meet the test requirements (flatness < 0.02 mm). Finally, artificial composite rock samples with standard geometric shapes and controllable fracture parameters are obtained, which are suitable for experimental tests such as shear strength, splitting tensile, and CT scanning.

[0080] The method of the present invention can be used to prepare fractured composite rock.

[0081] Evidence related to the technical effects obtained in the embodiments of the present invention.

[0082] Uniaxial compression tests are respectively carried out on the rock samples with fractures located in rock 1, rock 2, and the middle of the interface to obtain their stress-strain curves. (The fracture lengths are 0 mm, 5 mm, 10 mm, 15 mm, and 20 mm respectively).

[0083] Analysis: The present invention provides a method for preparing a fractured composite rock with controllable structure and adjustable position. Through the structural transformation of a 150 mm × 150 mm × 150 mm cube mold and the introduction of an embedded partition system, precise control of three typical layout methods of fractures in the middle of the rock-like material, at the interface, and inside another component is achieved. Compared with the fracture deviation of the samples obtained by the traditional manual insertion or later cutting method reaching ±5 mm, the fracture positioning error of this method is controlled within ±0.5 mm, and the fracture alignment rate reaches more than 96%. This greatly improves the standardization and repeatability of sample preparation, providing a basic guarantee for carrying out systematic comparative experiments.

[0084] In terms of fracture channel construction, the present invention combines wire cutting processing accuracy (<0.1 mm) with hot melt through-mold technology, and cooperates with high-strength steel plate partitions and steel sheet positioning devices to make the geometric shape of the fracture channels more regular. Compared with the rock-like fracture samples without using this process, experiments show that the standard deviation of the peak stress of the prepared samples is reduced by about 35%, and the distribution of strain limits is more concentrated, significantly reducing the data fluctuation caused by inconsistent fracture shapes and improving the credibility of experimental comparison.

[0085] The prepared cracked composite rock specimens show distinct differences in mechanical responses under different crack layouts. For example, when the crack is located in Rock 1, the peak stress can reach 55 MPa, while when the crack is located at the interface, it drops to approximately 40 MPa, and the failure process is more abrupt, with a significantly accelerated energy dissipation rate. This response trend fully demonstrates that the specimens prepared by this method have a high degree of reduction in simulating the crack action mechanism of natural rock masses and are suitable for in-depth studies on rock mechanical stability, failure mechanisms, and crack evolution processes.

[0086] In addition, the present invention adopts a modular assembly design, and the crack parameters (length range 5–30 mm, angle range 15°–75°) and their spatial positions can be flexibly adjusted to quickly adapt to the test requirements in different research scenarios. Compared with the traditional one-time processing method of custom molds, the sample preparation efficiency of this method is increased by about 40%, and the degree of freedom in test design is significantly enhanced, promoting the crack-type rock mechanics test from inefficient repetition to structured, quantifiable, and data-driven research, with good engineering promotion prospects and scientific research expansion potential.

[0087] As described above, it is only the specific implementation manners of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A method for preparing a composite rock with cracks, characterized in that, Including: (1) Provide a cubic mold and set a detachable partition in the center of the mold interior to form an interface structure of a rock-like sample; (2) According to the set fracture parameters, prefabricate fracture channels in the corresponding areas of the mold and insert positionable fracture forming members; (3) Inject the prepared rock-like slurry into the mold respectively, and let it stand for molding after vibrating and exhausting; (4) According to the required fracture position, adjust the position of the partition or insert piece to obtain a composite rock sample with a predetermined structure; (5) After curing and solidifying, demold, and finally obtain a standard cylindrical rock sample with a prefabricated fracture structure through processing procedures such as core drilling, cutting, and grinding.

2. The method according to claim 1, wherein The positionable fracture forming member includes a high-strength steel plate fracture positioning base obtained by wire cutting, a solid nylon buckle with a diameter of 30 mm and a height of 15 mm, and a steel sheet treated by surface sandblasting. The fracture positioning device assembled by the three can achieve geometric consistency control of the fracture morphology and precise position adjustment.

3. The method according to claim 1, characterized in that The method for preparing the fractured composite rock specifically includes the following steps: Step 1: Modify a 150 mm×150 mm×150 mm cubic plastic mold, draw a groove in the center of the mold interior, and place a 180 mm×155 mm×1 mm high-strength steel plate as a detachable partition to obtain a mold 1 for forming a rock-like composite sample; Step 2: Use Microsoft Visio drawing software to draw fracture parameter diagrams with different fracture dip angles, lengths, and positions, print them at a 1:1 ratio, position and paste them on the outer surface of the mold, and use a heated steel sheet to perform bilateral synchronous melting at specific fracture positions to form prefabricated fracture channels, insert steel sheets, and obtain a mold 2 with fractures in the middle of the rock-like material; Step 3: Prepare a fracture positioning base by wire cutting the high-strength steel plate, cooperate with a solid nylon buckle with a height of 15 mm and a diameter of 30 mm, and assemble with a steel sheet treated by surface sandblasting to form a fracture positioning device; Step 4: Evenly apply release oil on the inner surfaces of mold 1 and mold 2, prepare slurry according to the rock-like material mix ratio, fill the slurry into the molds respectively, and place them on a vibrating table for 15 seconds of oscillation; Step 5: After oscillation, let it stand for 30 minutes, draw out the partition in mold 2 to obtain a cubic specimen with fractures in the middle of the rock-like material; slowly insert the steel sheet of the fracture positioning device into mold 1 according to the position of the steel plate and the mold to obtain a cubic specimen with fractures at the interface; Step 6: 24 hours after pouring is completed, use an air pump to blow air at the bottom of the mold for demolding, cure for 28 days, take cores with a core drill, cut the ends, and polish to obtain a standard cylindrical rock sample with fractures of Φ×h = 50 mm×100 mm.

4. The preparation method of the composite rock with cracks according to claim 3, characterized in that, In the said Step 1, the depth of the groove at the bottom and on the side is 5 mm, and the width is 1.0±0.2 mm.

5. The preparation method of the composite rock with cracks according to claim 3, characterized in that In the said Step 2, in the dimensions of the steel sheet, L is the fracture length, the length is 180 mm, and the thickness is 1.0±0.2 mm.

6. The preparation method of the composite rock with cracks as claimed in claim 3, characterized in that, In the said Step 3, the length of the guiding slot of the fracture positioning base is equal to the fracture length L, the angle is equal to the fracture dip angle α, and the width is 1.0±0.2 mm; In Step 3, the steel sheet penetrates through the nylon buckle and the steel sheet. The nylon buckle is located on one side of the steel sheet, and the length of the other side of the steel sheet is 155 mm. In Step 4, in the dimensions of the steel sheet, L is the crack length, with a length of 180 mm and a thickness of 1 mm.

7. The preparation method of the composite rock with cracks as claimed in claim 3, wherein, In Step 5, the steel sheet is pulled out within 10 hours after pouring is completed, and the crack positioning device is removed.

8. The preparation method of the composite rock with cracks as described in claim 3, characterized in that, In Step 6, during the cutting process, the lengths of both types of rock samples are 50 mm, and the total length is 100 mm.

9. A production system for fractured composite rock implementing the production method of fractured composite rock according to any one of claims 1-8, characterized in that, The preparation system for the fissured composite rock includes: A transformation module for transforming a 150 mm×150 mm×150 mm cubic plastic mold. A groove is marked at the central position inside the mold, and a 180 mm×155 mm×1 mm high-strength steel plate is placed as a detachable partition to obtain a mold 1 for forming a rock-like composite sample. A drawing module for using Microsoft Visio drawing software to draw crack parameter diagrams with different crack inclinations, lengths, and positions. After printing at a 1:1 ratio, they are positioned and pasted on the outer surface of the mold. A heated steel sheet is used to perform bilateral synchronous heat fusion at specific crack positions to form a prefabricated crack channel, and a steel sheet is inserted to obtain a mold 2 with the crack located in the middle of the rock-like material. A cutting module for preparing a crack positioning base by wire cutting the high-strength steel plate, assembling it with a solid nylon buckle with a height of 15 mm and a diameter of 30 mm, and a steel sheet with sandblasted surface to form a crack positioning device. An oscillation module for evenly applying a release agent on the inner surfaces of mold 1 and mold 2, preparing a slurry according to the rock-like material mixing ratio, filling the slurry into the molds respectively, and placing them on a vibrating table for oscillation for 15 seconds. A static module for statically setting for 30 minutes after oscillation, pulling out the partition in mold 2 to obtain a cubic specimen with the crack located in the middle of the rock-like material; slowly inserting the steel sheet of the crack positioning device into mold 1 according to the position of the steel plate and the mold to obtain a cubic specimen with the crack located at the interface. A demolding module for, 24 hours after pouring is completed, using an air pump to blow air at the bottom of the mold for demolding, curing for 28 days, taking cores by a core drill, cutting the ends, and polishing to obtain a standard cylindrical rock sample with a crack, having Φ×h = 50 mm×100 mm.

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