A method for manufacturing a rock test piece with controllable morphology

Abstract

The application provides a rock sample manufacturing method with controllable topography, comprising parameterized definition of interface roughness; constructing a three-dimensional rough interface model in a sine wave function superposition manner according to a target fluctuation height parameter H and an overall representative slope S̄; establishing a counterform inner mold geometric model which is counter-shaped with the target interface according to the three-dimensional rough interface function surface, and 3D printing the counterform inner mold; pouring the rock sample by using the counterform inner mold and the outer mold; the application can directly design the interface topography according to the target parameters without relying on a real rock object, and realizes active, controllable and equivalent adjustment of the interface roughness; the counterform inner mold solves the efficient demolding problem of the complex reverse occlusion three-dimensional fluctuation interface.

Description

Technical Field

[0001] This application relates to the field of geotechnical engineering technology, and in particular to a method for preparing rock specimens with controllable morphology. Background Technology

[0002] Current research on the shear resistance of rock-concrete interfaces typically employs direct shear tests on natural rock interface specimens or artificially roughened specimens. While natural rock interfaces can reflect certain realistic morphological characteristics, their surface undulations exhibit significant randomness. Different specimens show substantial differences in peak and valley heights, slope distribution, spatial undulation direction, and local unevenness details, leading to large dispersion in test results and making it difficult to establish a comparative test group with good repeatability. Therefore, existing methods often employ artificially fabricated two-dimensional striped toothed surfaces, unidirectional sawtooth surfaces, or simple regular corrugated surfaces to simulate natural rough interfaces. However, these methods usually only reflect undulation characteristics in a single direction and are insufficient to characterize the three-dimensional spatial undulation characteristics of natural rock surfaces. Furthermore, the lack of a clear quantitative correspondence between roughness parameters and interface geometry makes it difficult to achieve designable and equivalent interface roughness.

[0003] For molding complex three-dimensional undulating interfaces, traditional machined molds or integral embedded molds still have problems such as complex processing, high cost, and difficulty in demolding. In particular, for rough interfaces with reverse interlocking characteristics, it is not easy to remove the integral inner mold smoothly after the specimen is molded, which can easily damage the already formed interface morphology and affect the accuracy of subsequent tests.

[0004] To address the aforementioned issues, existing research has employed high-precision point cloud data of the surface morphology of natural rock structural surfaces using 3D scanners. This data is then used to reconstruct the natural structural surfaces and virtual shear models containing them using reverse engineering software. Finally, PLA (polylactic acid) molds simulating the natural structural surfaces are fabricated using 3D printing technology. These molds are then used to cast similar materials into shear specimens within a sample preparation box (e.g., Xiong Zuqiang, Jiang Quan, Gong Yanhua, et al., "Method for Preparing Rock Mass Natural Structural Surface Specimens Based on 3D Scanning and Printing and Shear Test Verification," Rock and Soil Mechanics, Vol. 36, No. 6, 2015). However, while this method achieves reproducible structural surfaces, its interface morphology originates from a reverse scan of a real rock structural surface, requiring the acquisition of physical structural surfaces. This makes it difficult to perform forward, parametric active design and equivalence according to pre-set roughness indices. Furthermore, the use of monolithic structural surface molds can easily damage the formed morphology during demolding for 3D undulating interfaces with reverse interlocking characteristics, and it is also difficult to simultaneously construct structural surfaces on multiple surfaces of the same specimen.

[0005] Therefore, there is an urgent need to propose a method for preparing rock specimens that can parametrically describe the rough interface of rocks, controllably prepare three-dimensional undulating morphology, and repeatedly replicate the specimens. Summary of the Invention

[0006] The purpose of this application is to provide a method for preparing rock specimens with controllable morphology, so as to solve or alleviate the problems existing in the prior art.

[0007] To achieve the above objectives, this application provides the following technical solution: A method for preparing rock specimens with controllable morphology includes the following steps: S1. Parametric definition of interface roughness: The rough interface of the rock to be simulated is defined as a three-dimensional undulating surface z=f(x,y), using the undulation height parameter H, the local slope S(x,y), and the global representative slope. Characterizes the geometric features of the interface; S2. Construct a 3D rough interface model: Based on the target undulation height parameter H and the overall representative slope. Then, a three-dimensional rough interface model is constructed by superimposing one or more sets of sinusoidal functions. The interface function is represented as follows: ; in: The number of sine wave groups participating in the superposition; For the first The amplitude of a group of sine waves is used to control the contribution of the fluctuation height of that group of waveforms; For the first A group of sine waves in Period in direction; For the first A group of sine waves in Period in direction; For the first A group of sine waves in Phase in direction; For the first A group of sine waves in Phase in direction; S3. Based on the three-dimensional rough interface function surface constructed in step S2, establish a geometric model of the inverse inner mold that is the opposite of the target interface, and 3D print the inverse inner mold; the inverse inner mold is composed of several sub-modules, and adjacent sub-modules are connected by connecting ribs, with a weak section preset at the root of the connecting rib. S4. Specimen molding: Place the inverted inner mold at the designated position in the outer mold and pour the rock specimen material; after the rock specimen reaches the predetermined initial strength, remove the outer mold and the inverted inner mold to obtain the target rock specimen.

[0008] Furthermore, in step S1, H=z max -z minLet S(x,y) be the height difference between the highest and lowest points of the interface; the local slope S(x,y) is defined as: ; Overall, representing the slope The average area of ​​the local slope within the interface projection region A is: ; In the above formula, x and y are two-dimensional coordinates in the reference plane, z is the undulation height at the corresponding position, and the positive direction of the z-axis points in the direction of the rock protrusion.

[0009] Furthermore, the reverse-shaped inner mold has a segmented or block-shaped structure and is equipped with a demolding handle. The demolding handle is connected to each connecting rib by a thin wire; the thin wire is embedded in the connecting rib.

[0010] Furthermore, the inverted inner mold is a three-dimensional block structure, composed of several sub-modules arranged in a matrix.

[0011] Furthermore, the sub-modules may have the same or different dimensions.

[0012] Furthermore, the submodule is provided with a gripper on the back, making it easy to pick up the submodule by hand or with a tool.

[0013] Furthermore, for rock specimens with multiple non-parallel structural surfaces inside, fabrication is carried out using an outer mold and a reverse-shaped inner mold, including the following steps: First, a block-shaped inverted inner mold composed of several sub-modules is made. The five sides of the inverted inner mold are the inverted undulating rough surfaces of the rock side matrix, and one side is a flat surface. Adjacent sub-modules are joined together by connecting ribs so that the sub-modules form a weak cross section at the root. The inverted inner mold has reserved channels or at least two central sub-modules that do not contact the rock side matrix material. Place the flat side of the inverted inner mold into the outer mold, pour the rock matrix material, and after curing, remove the inner mold to obtain a rock specimen with the specified shape. When removing the inverted inner mold, first reverse the direction of the outer mold so that the flat side of the inverted inner mold faces upward. If there are two central sub-modules, remove them first. Then remove each sub-module in the order from the midpoint to the corner and from top to bottom.

[0014] Furthermore, for rock-concrete composite specimens with multiple non-parallel structural surfaces, the following steps are taken to fabricate them using a wrap-around inversion forming mold and a casting mold: First, a wrap-around inverted forming mold composed of five inverted sub-modules is constructed. The five inverted sub-modules include four side blocks and one bottom block. After being assembled, they form a cavity with an open top. The inner surface of the cavity is the inverted undulating rough surface of the four sides and bottom of the concrete core, while the outer surface is flat. Each inverted sub-module is divided into 2-9 small modules. Adjacent small modules are joined by connecting ribs, and a weak section is set at the root of the connecting ribs. A 4mm wide cosine transition zone is set at the edge where adjacent sides meet so that the undulating surface gradually converges into a flat surface. Concrete side material is poured into the wrap-around inverted forming mold and cured. After demolding, the concrete core is obtained. The concrete core is placed in the casting mold, and the concrete core is supported by positioning blocks. Then, the rock side matrix material is poured. After curing to the predetermined strength, the core is demolded from the outer mold to obtain a rock-concrete composite specimen with multiple non-parallel rough interfaces.

[0015] Furthermore, for rock specimens with multiple parallel three-dimensional undulating structural surfaces, the following steps are taken to fabricate them using an outer mold and a reverse-shaped inner mold: First, multiple sets of reverse-shaped inner molds are made as needed. The reverse-shaped inner mold is a thick plate with one side being a reverse-shaped undulating rough surface and the other five sides being flat surfaces. The reverse-shaped inner mold consists of 9 sub-modules arranged in a planar matrix. Adjacent sub-modules are joined together by connecting ribs so that the sub-modules form a weak section at the root. The first layer of rock side matrix material is quantitatively poured into the outer mold, and the first set of inverted inner molds is pressed on top of it. After it reaches the predetermined initial strength, the first set of inverted inner molds is removed, forming the first three-dimensional undulating structural surface on the top surface of the first layer of rock side matrix. Then, the next layer of rock side matrix material is quantitatively poured into this structural surface and the corresponding inverted inner mold is pressed on top. The above pouring, pressing and demolding steps are repeated to form the second structural surface. The above steps are repeated until a rock specimen with the target number of three-dimensional undulating structural surface surfaces is obtained.

[0016] The technical solution of this application has the following beneficial effects: This application transforms the random roughness characteristics of natural rock interfaces into a quantitatively designable three-dimensional undulation parameter system. By establishing a parameterized expression for the rough interface through the undulation height parameter H and the slope parameter S, interface roughness can be quantitatively described, actively designed, and repeatedly implemented. Simultaneously, it employs the superposition of multiple sets of sine waves to construct a three-dimensional rough interface, overcoming the limitations of existing two-dimensional striped and unidirectional sawtooth interfaces that can only reflect undulations in a single direction. This approach can describe multi-directional spatial undulation characteristics and, through parameter adjustment, achieve interface morphology structures of different scales and complexities, more closely approximating the true spatial characteristics of natural rock surfaces. Compared to methods that use 3D scanning to inversely reconstruct the structure of real rock surfaces, this application does not rely on a specific real rock sample; it can directly design the interface morphology based on target parameters, achieving active, controllable, and equivalently adjustable interface roughness.

[0017] This application solves the problem of efficient demolding of complex reverse-interlocking three-dimensional undulating interfaces by using a 3D-printed, segmented, inverted inner mold with a weak cross-section and demolding handle. Existing monolithic inner molds are difficult to remove completely in complex interface scenarios, while this application significantly reduces demolding difficulty through a controllable separation and sequential withdrawal mechanism. Furthermore, it allows for the simultaneous construction of structural surfaces on multiple surfaces of the same rock specimen, thus supporting various experimental requirements such as single-surface direct shear, multi-jointed rock mass shear, and multi-faceted rock-concrete bonding. This application possesses strong repeatability, comparability, and scalability, with a wider range of applications and greater design flexibility. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein: Figure 1 This is a schematic diagram of the structure of the reverse-shaped inner mold in Embodiment 1 of the present invention.

[0019] Figure 2 This is a schematic diagram of the rock-concrete composite specimen of Embodiment 1 of the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of a multi-jointed rock specimen according to Embodiment 2 of the present invention.

[0021] Figure 4 This is a schematic diagram of the rock-concrete composite specimen of Embodiment 3 of the present invention.

[0022] Figure 5 This is a schematic diagram of the structure of the wrap-around reverse forming mold of Embodiment 3 of the present invention.

[0023] Figure 6 This is a cross-sectional schematic diagram of the reverse-shaped inner mold of Embodiment 4 of the present invention.

[0024] Figure 7 The images are simulation diagrams of rough interface morphology obtained by calculating the interface function and parameters according to Embodiments 1-3 of the present invention; wherein, (a) and (b) are simulation diagrams of the rough interface morphology of Embodiments 1 and 2, respectively, and (c) is the unfolded morphology of the five rough interfaces of Embodiment 3.

[0025] Explanation of reference numerals in the attached figures: 1-Submodule, 2-Grab, 3-Connecting rib, 4-Outer mold, 5-Small module, 100-Concrete side matrix, 200-Rock side matrix, 301-First structural surface, 302-Second structural surface, 400-Concrete core. Detailed Implementation

[0026] The overall concept of this invention can be summarized as follows: First, in the interface design stage, the rough interface of natural or target rock is abstracted into a three-dimensional undulating surface, and its roughness is quantitatively characterized by the undulation height parameter H and the slope parameter S; Second, in the interface implementation stage, a corresponding inverse inner mold is generated based on the established three-dimensional undulation function surface, and a 3D printed inner mold with a weak cross section and a demolding handle is used to complete the rock specimen, thereby obtaining a batch of geometrically consistent specimens.

[0027] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present application encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0028] A method for preparing rock specimens with controllable morphology includes the following steps: S1. Parametric definition of interface roughness: First, the rough rock interface (structural surface) to be simulated is defined as a three-dimensional undulating surface z=f(x,y), where x and y are two-dimensional coordinates in the reference plane, z is the undulation height at the corresponding position, and the positive direction of the z-axis points to the direction of rock protrusion.

[0029] To facilitate quantitative control of roughness, the undulation height parameter H, the local slope S(x,y), and the overall representative slope are used. Characterizing the geometric features of the interface. The undulation height parameter H is used to characterize the overall peak-valley undulation amplitude of the interface, defined as the height difference between the highest and lowest points of the interface, i.e., H = z. max -z min .

[0030] The local slope S(x,y) is used to characterize the degree of undulation of the interface within a unit horizontal distance at location (x,y), and is defined as: (1); To characterize the rate of change of the entire interface's undulations, a global representative slope is defined. Let A be the average area of ​​the local slope within the interface projection region A, i.e.: (2); H reflects the amplitude characteristics of the interface. It reflects the average rate of change across the entire interface; if necessary, it can also record the maximum or quantile of local slope to limit local steep slopes. It represents the overall slope. The value should be controlled within the range of 0.45-0.65, with a preferred value of 0.55. This parameter range allows the interface to have a certain locking ability, while reducing the difficulty of molding or demolding caused by excessively steep local slopes.

[0031] Using the above parameters, the complex random morphology of natural rock surfaces can be transformed into a calculable and controllable parameter system. Among them, H controls the overall fluctuation amplitude. By controlling the overall average rate of change, the local slope S(x,y) is used to check the location of steep slopes, so that the subsequent interface design can be actively constructed according to the test objectives.

[0032] S2. Construct a three-dimensional rough interface model: After obtaining the target undulation height parameter H and the overall representative slope Then, a three-dimensional rough interface model is constructed by superimposing one or more sets of sinusoidal functions. The interface function is represented as follows: ; in: The number of sine wave groups participating in the superposition; For the first The amplitude of a group of sine waves is used to control the contribution of the fluctuation height of that group of waveforms; For the first A group of sine waves in Period in direction; For the first A group of sine waves in Period in direction; For the first A group of sine waves in Phase in direction; For the first A group of sine waves in Phase in direction; By adjusting the amplitude, period, phase, and number of superimposed groups of each set of sine waves, the macroscopic and local microscopic undulation characteristics of the interface can be jointly controlled, thereby constructing a three-dimensional interface morphology with different roughness and spatial undulation characteristics.

[0033] Compared with conventional two-dimensional sawtooth or unidirectional corrugated interfaces, the above method can more realistically reflect the three-dimensional spatial undulation characteristics of natural rock interfaces. Furthermore, since the model parameters are clear and can be adjusted independently, it is convenient to carry out single-factor or multi-factor analysis, such as studying the influence of amplitude, period, phase, and waveform superposition levels on shear resistance.

[0034] S3, 3D printing to create reverse-shaped inner mold; A mold set includes an outer mold, a reverse-shaped inner mold, and positioning blocks. The outer mold has a regular shape, such as a cuboid or cylinder. The positioning blocks are placed inside the outer mold as needed to support the reverse-shaped inner mold at a designated position within the outer mold. Based on the three-dimensional undulating interface function surface for the target rock constructed in step S2, a geometric model of the reverse-shaped inner mold, which is the opposite of the target interface, is established, and the reverse-shaped inner mold is 3D printed.

[0035] The reverse-shaped inner mold has a segmented or block-shaped structure. After the specimen is formed, the inner mold can be separated into several sub-modules through a preset fracture path, thereby gradually removing it and avoiding damage to the already formed complex and rough interface when pulling it out as a whole. Preferably, the reverse-shaped inner mold has a three-dimensional block structure, dividing the inner mold into several sub-modules in m rows × n columns along the interface plane. The sub-modules can be divided evenly or according to the shape characteristics of the target interface to facilitate demolding. Adjacent sub-modules are connected by connecting ribs, and a weak section is preset at the root of the connecting ribs, so that the inner mold breaks or separates at a predetermined position when being pulled out, allowing the sub-modules to be separated piece by piece. This makes it easier for personnel to control the inner mold to separate and exit in a preset order, thereby improving the demolding efficiency and forming accuracy of complex reverse interlocking interfaces. The three-dimensional undulating interface can be set on a single interface of the specimen (such as the upper and lower interfaces between two matrices) or on multiple surfaces of the rock specimen (such as the four sides and bottom of the central rock core). Thus, under the same technical framework, it is possible to prepare rock-concrete shear specimens with a single structural surface, as well as multi-jointed rock mass specimens with multiple structural surfaces and rock-concrete multi-faceted bonding specimens with multi-faceted interlocking characteristics.

[0036] S4. Specimen molding: The specimen molding process includes rock specimen molding and inner mold demolding. First, the 3D-printed inverted inner mold is placed in the designated position within the outer molding die, and the rock specimen is then cast or molded. For single-surface structural simulation, the inverted inner mold can be placed directly at the bottom of the outer mold, and then the rock specimen material is poured on top of the inverted inner mold. The rock specimen material can be suitable materials such as rock simulation materials and cement mortar, depending on the experimental conditions.

[0037] Once the rock specimen has reached the predetermined initial strength, the inner mold is removed. Specifically, for specimens with a single structural surface, the bottom cover plate of the outer mold is removed, and then the sub-modules of the inverted inner mold are removed one by one.

[0038] For rock specimens with multiple non-parallel structural surfaces, there are two ways to construct the inverted inner mold: First, the inverted inner mold is removed from the inside of the molded specimen. In this case, the inverted inner mold is a three-dimensional block structure with a reserved channel or at least two central sub-modules that do not contact the specimen. These two modules are removed first, forming a central channel within the inverted inner mold. The reserved channel and the central channel provide space for other sub-modules to move laterally and detach from the specimen. Then, each sub-module is removed sequentially from the outside in. Second, the inverted inner mold is peeled off from the outer periphery of the cast rock specimen. This segmented demolding method effectively avoids localized interface damage, edge destruction, or detail distortion caused by overall demolding. To facilitate the removal of sub-modules during removal, grippers are provided on the back of the sub-modules. These grippers can be ring-shaped, hook-shaped, mushroom-shaped, T-shaped, or club-shaped, allowing for easy removal by hand or tools.

[0039] To produce a rock-concrete composite specimen, after the target structural surface on the rock side is formed, a concrete substrate is poured into the outer mold on the structural surface, or a layer-by-layer printing method is used to form the concrete material, thereby obtaining the rock-concrete composite specimen.

[0040] For direct shear testing, the molded rock-concrete composite specimens are cured to the predetermined age and then installed in a direct shear testing apparatus. A predetermined normal load is applied first, followed by a shear load along the interface direction. During the test, shear force, relative slip displacement, and interface failure mode are recorded, and evaluation indicators such as peak shear strength, residual shear strength, and shear stiffness are obtained.

[0041] Example 1 This embodiment provides a rock-concrete composite specimen with a single structural surface. The purpose is to obtain a set of rock specimens with consistent geometry, controllable roughness, and repeatability, and then to produce a rock-concrete composite specimen.

[0042] In this embodiment, the overall dimensions of the composite specimen are set to 100mm × 100mm × 100mm, with the interface plane dimensions also being 100mm × 100mm. The specimen consists of two parts: a lower rock matrix and an upper concrete matrix, with an artificially simulated three-dimensional undulating shear interface in between. The rock matrix has a height of 50mm, and the concrete matrix has a height of 50mm. The plane containing the interface (reference plane) is located at the center of the specimen's height.

[0043] A method for preparing rock specimens with controllable morphology includes the following steps: S1. Parametric definition of interface roughness: The target interface (the interface between the rock-side matrix and the concrete-side matrix, which is also the structural surface of the rock-side matrix) is defined as a three-dimensional undulating surface z=f(x,y), where x and y are the coordinates in the interface plane, and z is the undulation height at the corresponding coordinates. The undulation height parameter H and the overall representative slope are used. The roughness characteristics of the interface are quantitatively characterized, and local steep slopes are examined using the local slope S(x,y). In this embodiment, the undulation height parameter of the target interface is taken as H=z. max -z min =12mm, the overall target represents the slope. Set it to 0.55.

[0044] S2. Construct a three-dimensional rough interface model: A three-dimensional undulating interface function is constructed by superimposing two sets of sine waves to simultaneously simulate macroscopic and local microscopic undulations. The expression for the interface function is: ; The values ​​for each group of parameters are as follows: The first set of waveform parameters are: ; The second set of waveform parameters are: ; The first set of waveforms is used to control the overall undulation profile of the interface, forming a large-scale peak-valley structure. The second set of waveforms is used to introduce local micro-undulations based on the first set of macro-profiles to increase the spatial complexity of the interface. The elevations of discrete nodes within a 100mm × 100mm range of the functional surface are calculated at 1mm intervals, and the maximum, minimum, and local slopes are statistically analyzed. The undulation height H is approximately 11.70mm, and the overall representative slope is... The value is approximately 0.55, which is basically consistent with the preset target value. Therefore, the function surface meets the design requirements. The function surface formed using the above conditions is as follows: Figure 7 As shown in (a) of the diagram.

[0045] S3, 3D printing to create reverse-shaped inner mold; Based on the aforementioned three-dimensional undulating interface function surface, an inner mold geometric model that is the inverse of the target interface is established. Specifically, within a 100mm × 100mm plane, the constructed z(x,y) surface is used as the top surface of the interface, and then stretched downwards along the height direction to form a three-dimensional inverse inner mold body with a certain height. To facilitate subsequent demolding, such as... Figure 1As shown, in this embodiment, the inner mold adopts a three-dimensional segmented structure: with the center of the interface plane as the reference, two mutually perpendicular vertical dividing surfaces are set along the x and y directions respectively, dividing the inner mold into 3 rows × 3 columns, totaling 9 sub-modules. Each sub-module supports the reverse undulating surface of the corresponding area above it. Adjacent sub-modules are connected into a whole by several connecting ribs, and a weak section is preset at the root of the connecting rib. The thickness of the weak section is 1.2mm, that is, the connecting rib is the easy breakage point. The inner mold material is preferably PLA or photosensitive resin 3D printing material. The printing layer height is controlled at 0.15mm-0.20mm to ensure that the detailed geometry of the rough interface can be accurately reproduced by printing. After printing, the surface of the inner mold is slightly sanded and cleaned to remove support residues and burrs, but without changing the target undulating morphology.

[0046] S4. Specimen molding: The outer mold is a square steel mold with an inner cavity size of 100mm × 100mm × 60mm. A release agent is applied to the inner surface of the outer mold. Then, the reverse-shaped inner mold is placed inside the outer mold, back side down, and the rock-side matrix material is poured. After curing for 24 hours, once the matrix reaches the predetermined initial strength (compressive strength of the rock-side matrix exceeding 5MPa), the inner mold is demolded. The cover plate of the outer mold located on the inner mold side is removed, and then the sub-modules are removed one by one.

[0047] To facilitate the removal of sub-modules, a gripper is provided on the back of each sub-module, along with a demolding handle. The demolding handle is connected to each connecting rib via a thin wire. During 3D printing, the thin wire is embedded in the connecting ribs. Pulling the demolding handle pulls the wire, causing the connecting ribs to break, allowing the inverted inner mold to separate first along the weakest section. The sub-modules then separate individually, and each block is removed sequentially. Ideally, the sub-modules should be removed in the order of the center first, then the edges. Alternatively, if a thin wire is not used, the connecting ribs can be broken by forcefully moving the sub-module, causing it to separate. The thin wire can be fishing line, stainless steel microfilament, or stainless steel microfilament stranded wire, with a diameter preferably less than 0.5 mm.

[0048] After the reverse mold is completely removed, a three-dimensional undulating rough surface consistent with the target interface will be formed on the rock side matrix. The interface surface is then observed and cleaned to remove loose particles and residual release agent. If necessary, the surface can be lightly brushed with a soft brush.

[0049] To verify the molding accuracy, vernier calipers, profile gauges, 3D scanners, or photographic measurement methods were used to check the peak-valley height differences at several representative locations on the interface. If the deviation between the interface peak-valley height differences and the design value is controlled within ±10%, the molding is considered to meet the requirements.

[0050] After the target structural surface on the rock side is formed, it is placed in an outer mold, concrete is poured on it, and it is cured in a standard curing environment for 28 days to produce a rock-concrete composite specimen, as shown in the schematic diagram. Figure 2 As shown. At least three parallel specimens should be prepared for each set of interface parameters to statistically analyze the dispersion and repeatability of the interface shear properties.

[0051] In this embodiment, to facilitate better filling of the uneven parts of the rough interface, the rock side matrix is ​​prepared using rock-simulated mortar, with the raw material mass ratio being: ordinary silicate cement: quartz sand: water = 1:2.5:0.45; fine aggregate concrete is preferably used, with the raw material ratio being: cement: sand: fine aggregate: water = 1:1.5:1.2:0.42.

[0052] Compared to an integral inner mold, this embodiment significantly reduces demolding resistance at complex reverse interlocking interfaces, minimizing the risk of interface damage. Furthermore, the sub-modules in this embodiment are reusable. Specifically, a liner with adhesive or slots that fit the sub-module is taken, the sub-module is cleaned on the liner, and then assembled as before to obtain the original reverse inner mold with the desired shape.

[0053] Example 2 This embodiment 2 provides a method for preparing a multi-jointed rock specimen containing multiple parallel three-dimensional undulating structural planes. Unlike embodiment 1, which only contains a single structural plane, this embodiment sets two mutually parallel three-dimensional undulating structural planes along the height direction inside the same specimen to simulate a rock mass containing multiple joints and to study the effects of joint roughness and joint spacing on the overall shear resistance of the rock mass. All other aspects are the same as in embodiment 1.

[0054] like Figure 3 As shown, the overall dimensions of the specimen in this embodiment remain 100mm × 100mm × 100mm. It is divided into three layers of rock matrix from bottom to top along the height direction. An artificially simulated three-dimensional undulating structural surface is set between each adjacent layer, meaning the specimen contains two parallel structural surfaces that divide it into a lower, middle, and upper layer. Each layer is approximately 33mm high, and the normals of both structural surfaces are perpendicular to the shear loading direction. By adjusting the pouring height of each layer, the joint spacing can be changed within the range of 20mm-40mm. Within the same technical framework, the number of structural surfaces can be expanded to three or more to simulate denser joint groups. The following explanation uses two structural surfaces as an example.

[0055] Both structural surfaces in this embodiment use the same interface function as in Embodiment 1. The first (lower) structural surface has its function height amplitude normalized to H1=12mm, and the calculated overall representative slope... Approximately 0.55; the second (upper) structural surface amplifies the spatial frequencies in the x and y directions by a factor of 1.054 and normalizes the height amplitude to H2=8mm, resulting in the overall representative slope. Approximately 0.40. The target H and amplitude can be calibrated by adjusting the spatial frequency and amplitude, respectively. The function surface formed in this embodiment is as follows: Figure 7 As shown in (b) of the embodiment. In this embodiment, two sets of three-dimensional segmented inverse inner molds are designed for the two structural surfaces respectively. Each set of inverse inner molds is divided into 9 sub-modules according to a 3×3 grid. The sub-modules are connected by connecting ribs and a weak section with a thickness of about 1.2mm is set at the root. Its structure is the same as that of embodiment 1. The undulating surfaces (inverse undulating rough surfaces) of the two sets of inner molds are the inverse of the first and second structural surfaces of this embodiment, respectively.

[0056] The rock specimen with multiple parallel structural surfaces was formed using a layered casting and demolding process: First, a quantitative amount of the lower layer of rock matrix material was cast into the outer mold, and a first set of inverted inner molds was placed on top. After reaching the predetermined initial strength, the first set of inverted inner molds was removed, forming the first three-dimensional undulating structural surface on the top surface of the lower layer. Subsequently, the middle layer of rock matrix was cast onto this structural surface, and a second set of inverted inner molds was placed. The above casting, molding, and demolding steps were repeated to form the second structural surface. Finally, the upper layer of rock matrix was cast. The same rock simulation mortar as in Example 1 could be used for each layer. After molding, the specimen was cured for 28 days according to the curing regime of Example 1.

[0057] Example 3 This embodiment provides a rock-concrete composite specimen with multiple non-parallel rough interfaces. Three-dimensional undulating rough surfaces are simultaneously constructed on the four sides and bottom of the central matrix, which is then enclosed by an outer matrix. This simulates engineering scenarios where concrete and rock simultaneously interlock and bond at multiple contact surfaces, such as anchor bodies and rock-socketed piles. The following explanation uses a simulated rock-socketed pile as an example. In actual engineering, the borehole walls of rock-socketed piles are not smooth cylindrical surfaces; they are rough, uneven rock surfaces.

[0058] like Figure 4As shown, in this embodiment, the specimen consists of a central concrete core (concrete side matrix) and a surrounding rock side matrix. The core is approximately a cube of 60mm × 60mm × 60mm, with artificially simulated three-dimensional undulating structures on its four sides and bottom (five faces in total). The concrete core is surrounded and bottomed by a rock side matrix of approximately 20mm thickness, forming a multifaceted bonded specimen with overall dimensions of approximately 100mm × 100mm × 80mm. The top surface of the core is flush with the top surface of the specimen and exposed upwards, serving as the loading surface for subsequent push-out tests. The thickness of the rock side matrix is ​​adjusted within the range of 15mm-30mm. At least three parallel specimens are prepared for each set of interface parameters to statistically analyze the dispersion of the results.

[0059] Each rough surface of the core was constructed using the same interface function z(x,y) as in Example 1, with the undulation height H and the overall slope representing the gradient. Characterization was performed. In this embodiment, H = 10 mm was uniformly used for all surfaces. Approximately 0.50. In specific modeling, the spatial frequencies of the function in the x and y directions of Example 1 were uniformly adjusted to 0.936 times, and the height amplitude was normalized to 10mm. The phases of the four sides were shifted sequentially by 0, π / 4, π / 2, and 3π / 4, while the bottom phase was shifted by π / 6, ensuring that the shapes of each surface were unique. A 4mm wide cosine transition band was set at the edges where adjacent sides intersected, causing the undulating surface to gradually converge into a plane, thereby reducing stress concentration at the corners, printing distortion, and the risk of demolding and edge chipping. Figure 7 (c) shows the unfolded morphology of the five rough surfaces of the core.

[0060] This embodiment uses a wrap-around reverse forming mold. The mold surrounds the four sides and bottom of the concrete core from the outside to form multiple reverse undulating cavities on the outer surface; its structural position and demolding direction are different from the reverse inner molds in embodiments 1, 2 and 4.

[0061] The encapsulating inversion forming mold of this embodiment is composed of five inversion sub-modules, including four side blocks and one bottom block. After assembly, the five inversion sub-modules form a cavity with an open top. The inner surface of the cavity represents the inversion undulating surfaces of the four sides and bottom of the rock core, while the outer surface of the inversion sub-modules is either flat or equipped with grippers. Preferably, each inversion sub-module is further divided into 2-9 smaller modules, with adjacent smaller modules joined by connecting ribs, and a weak section is provided at the root of the connecting ribs. Its segmentation and piece-by-piece removal mechanism is the same as in Embodiment 1, the difference being that this mold encapsulates multiple surfaces of the rock core from the outside. Figure 5 The diagram schematically illustrates the encapsulated reverse forming mold. Concrete side material is poured into the encapsulated reverse forming mold, and after shaping and curing, the concrete core is obtained by demolding.

[0062] Then, in the casting mold, the concrete rock core was supported by positioning blocks, and then the rock side material was poured. After curing, the mold was demolded and cast to obtain a rock-concrete composite specimen with multiple non-parallel rough interfaces.

[0063] To verify the operability of the interface function representation method, the interface functions of Examples 1-3 were discretized using a 1mm grid, and the height amplitude was normalized according to the target H. Then, the local slope and the overall representative slope were calculated according to Equation (1) and Equation (2). Figure 7 The results shown are consistent with the H and values ​​set in each embodiment. Consistent. The resulting discrete height field can be further converted into a surface mesh and exported as an STL file for 3D printing reverse-forming molds.

[0064] Example 4 Unlike Example 3, which requires pouring a concrete rock core first and then pouring the rock side material into the mold, this example directly produces a rock specimen with multiple non-parallel rough interfaces inside using an outer mold and a reverse-shaped inner mold. The shape of the rock side matrix in Example 3 is used as an example for illustration.

[0065] like Figure 6 As shown, the inverted inner mold in this embodiment is a block composed of 27 sub-modules, with 9 modules per layer; five sides of the inverted inner mold are the inverted undulating rough surfaces of the rock matrix, and one side is a flat surface; adjacent sub-modules are joined together by connecting ribs so that the sub-modules form a weak cross-section at the root. The inverted inner mold in this embodiment is the first construction method of the inverted inner mold described above (in step S4).

[0066] When casting the rock side matrix, first place the inverted inner mold inside the outer mold with the flat surface of the inverted inner mold facing down, then cast the rock side matrix material, and let it stand until the compressive strength of the rock side matrix reaches more than 5MPa before removing the inner mold to obtain a rock specimen with the specified shape.

[0067] For ease of description, the sub-modules of the reverse inner mold are numbered. The sub-module with a flat surface is designated as the first layer, and the other two layers are designated as the second and third layers respectively. A represents the sub-modules at the four corners, B represents the sub-module located at the midpoint of the side, and C represents the sub-module located at the center of each layer. Then, C1 is the sub-module at the center of the first layer, B1 is the sub-module at the midpoint of the side of the first layer, A1 is the sub-module at the four corners of the first layer, and so on. Figure 6The figure shows a cross-sectional view along the mid-section of the rock specimen, with some sub-module numbers shown. Before removing the inner mold, the outer mold is turned upside down and the bottom cover is removed to expose the flat surface of the reverse-shaped inner mold. Then, C1 and C2 are removed to form the central channel. Due to the limitation of the reverse shape, B1 cannot be pulled out vertically. It needs to be moved horizontally until it is completely separated from the rock matrix before removing the outer mold. After removing the four B1 pieces, the four A1 pieces are removed in the same way. The second layer uses a similar sequence, first removing the four B2 pieces, then removing the four A2 pieces. In the third layer, C3 is pulled out first, and then B3 and A3 are removed in sequence. During demolding, the direction of the sub-module translation is adjusted according to the curved shape of the rough surface to avoid causing damage to the surface edges or local chipping of the rock specimen.

[0068] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing rock specimens with controllable morphology, characterized in that, Includes the following steps: S1. Parametric definition of interface roughness: The rough interface of the rock to be simulated is defined as a three-dimensional undulating surface z=f(x,y), using the undulation height parameter H, the local slope S(x,y), and the global representative slope. Characterizes the geometric features of the interface; S2. Construct a 3D rough interface model: Based on the target undulation height parameter H and the overall representative slope. Then, a three-dimensional rough interface model is constructed by superimposing one or more sets of sinusoidal functions. The interface function is represented as follows: ； in: The number of sine wave groups participating in the superposition; For the first The amplitude of a group of sine waves is used to control the contribution of the ripple height of that group of waveforms; For the first A group of sine waves in Period in direction; For the first A group of sine waves in Period in direction; For the first A group of sine waves in Phase in direction; For the first A group of sine waves in Phase in direction; S3. Based on the three-dimensional rough interface function surface constructed in step S2, establish a geometric model of the inverse inner mold that is the opposite of the target interface, and 3D print the inverse inner mold; the inverse inner mold is composed of several sub-modules, and adjacent sub-modules are connected by connecting ribs, with a weak section preset at the root of the connecting rib. S4. Specimen molding: Place the inverted inner mold at the designated position in the outer mold and pour the rock specimen material; after the rock specimen reaches the predetermined initial strength, remove the outer mold and the inverted inner mold to obtain the target rock specimen.

2. The method for preparing rock specimens with controllable morphology according to claim 1, characterized in that: In step S1, H=z max -z min Let S(x,y) be the height difference between the highest and lowest points of the interface; the local slope S(x,y) is defined as: ； Overall, representing the slope The average area of ​​the local slope within the interface projection region A is: ； In the above formula, x and y are two-dimensional coordinates in the reference plane, z is the undulation height at the corresponding position, and the positive direction of the z-axis points in the direction of the rock protrusion.

3. The method for preparing rock specimens with controllable morphology according to claim 1, characterized in that: The reverse-shaped inner mold has a segmented or block-shaped structure and is equipped with a demolding handle. The demolding handle is connected to each connecting rib by a thin wire; the thin wire is embedded in the connecting rib.

4. The method for preparing rock specimens with controllable morphology according to claim 1, characterized in that: The inverted inner mold is a three-dimensional block structure, composed of several sub-modules arranged in a matrix.

5. The method for preparing rock specimens with controllable morphology according to claim 1, characterized in that: The sub-modules may have the same or different dimensions.

6. The method for preparing rock specimens with controllable morphology according to claim 1, characterized in that: The submodule is equipped with a gripper on the back, making it easy to pick up the submodule by hand or with a tool.

7. The method for preparing rock specimens with controllable morphology according to claim 1, characterized in that: For rock specimens with multiple non-parallel structural surfaces inside, the following steps are taken to prepare them using an outer mold and a reverse-shaped inner mold: First, a block-shaped inverted inner mold composed of several sub-modules is made. The five sides of the inverted inner mold are the inverted undulating rough surfaces of the rock side matrix, and one side is a flat surface. Adjacent sub-modules are joined together by connecting ribs so that the sub-modules form a weak cross section at the root. The inverted inner mold has reserved channels or at least two central sub-modules that do not contact the rock side matrix material. Place the flat side of the inverted inner mold into the outer mold, pour the rock matrix material, and after curing, remove the inner mold to obtain a rock specimen with the specified shape. When removing the inverted inner mold, first reverse the direction of the outer mold so that the flat side of the inverted inner mold faces upward. If there are two central sub-modules, remove them first. Then remove each sub-module in the order from the midpoint to the corner and from top to bottom.

8. The method for preparing rock specimens with controllable morphology according to claim 1, characterized in that: For rock-concrete composite specimens with multiple non-parallel structural surfaces, the following steps are included in the fabrication process using a wrap-around inversion forming mold and a casting mold: First, a wrap-around inverted forming mold composed of five inverted sub-modules is constructed. The five inverted sub-modules include four side blocks and one bottom block. After being assembled, they form a cavity with an open top. The inner surface of the cavity is the inverted undulating rough surface of the four sides and bottom of the concrete core, while the outer surface is flat. Each inverted sub-module is divided into 2-9 small modules. Adjacent small modules are joined by connecting ribs, and a weak section is set at the root of the connecting ribs. A 4mm wide cosine transition zone is set at the edge where adjacent sides meet so that the undulating surface gradually converges into a flat surface. Concrete side material is poured into the wrap-around inverted forming mold and cured. After demolding, the concrete core is obtained. The concrete core is placed in the casting mold, and the concrete core is supported by positioning blocks. Then, the rock side matrix material is poured. After curing to the predetermined strength, the core is demolded from the outer mold to obtain a rock-concrete composite specimen with multiple non-parallel rough interfaces.

9. The method for preparing rock specimens with controllable morphology according to claim 1, characterized in that: For rock specimens with multiple parallel three-dimensional undulating structural surfaces, the following steps are taken to fabricate them using an outer mold and a reverse-shaped inner mold: First, multiple sets of reverse-shaped inner molds are made as needed. The reverse-shaped inner mold is a thick plate with one side being a reverse-shaped undulating rough surface and the other five sides being flat surfaces. The reverse-shaped inner mold consists of 9 sub-modules arranged in a planar matrix. Adjacent sub-modules are joined together by connecting ribs so that the sub-modules form a weak section at the root. The first layer of rock side matrix material is quantitatively poured into the outer mold, and the first set of inverted inner molds is pressed on top of it. After it reaches the predetermined initial strength, the first set of inverted inner molds is removed, forming the first three-dimensional undulating structural surface on the top surface of the first layer of rock side matrix. Then, the next layer of rock side matrix material is quantitatively poured into this structural surface and the corresponding inverted inner mold is pressed on top. The above pouring, pressing and demolding steps are repeated to form the second structural surface. The above steps are repeated until a rock specimen with the target number of three-dimensional undulating structural surface surfaces is obtained.

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