Rock-like test piece with pre-embedded seepage passage and / or gushing water cavity and preparation method thereof

Abstract

The application discloses a rock-like test piece with pre-embedded seepage channels and / or water gushing cavities and a preparation method thereof, and aims to solve the technical problem that the existing simulation test piece cannot truly simulate and clearly and visually observe the influence of water seepage in seepage channels and / or water gushing in water-rich cavities on surrounding rock and lining structure inside rock mass. The application uses high brittleness and transparency resin casting to simulate engineering rock mass, and embeds a tunnel and a model with pre-embedded seepage channels and water gushing cavities in the engineering rock mass based on an engineering site. The obtained rock-like test piece has the characteristics of transparency, easy observation, realization of various working condition combinations, high brittleness of rock, etc., can clearly observe the evolution law of seepage and water gushing under the action of load, and can be used for the research on the seepage mechanism of original seepage channels and the water gushing mechanism of water-rich cavities.

Description

Technical Field

[0001] This application relates to the field of rock mass model testing technology, specifically to a rock-like specimen with a pre-embedded seepage channel and / or a sudden water inrush cavity and its preparation method. Background Technology

[0002] With the continuous improvement and development of domestic transportation networks and water conservancy projects, the construction of railways, deep-buried mountain tunnels, and water conveyance and flood discharge tunnels is accelerating. The adverse geological environments in which these tunnels are located are also becoming increasingly complex (e.g., groundwater, karst, geothermal energy, gas, high ground stress, etc.). Among these, groundwater (pore water, fissure water, karst water) is a major cause of difficulties in tunnel construction and operation, and budget overruns. The presence of groundwater has a significant impact on tunnel construction and operation, mainly affecting the stability of the surrounding rock, the stress on the tunnel lining structure, and the tunnel operating environment. Groundwater reduces the strength of the surrounding rock through erosion, softening, and dissolution; groundwater seepage can alter the stress state of the lining structure, making structural calculations more complex; if groundwater penetrates cracks in the lining concrete and permeates the waterproofing and drainage system, it will severely damage the tunnel operating environment and increase costs. Constructing tunnels in areas rich in groundwater inevitably encounters high water pressure problems.

[0003] Due to the characteristics of tunnels and underground engineering, underground water-rich structures are a significant factor affecting the stability of surrounding rock and lining structures. The opacity of natural rock masses makes it impossible to directly observe the failure evolution of their internal structures. Traditional methods such as drilling, geophysical exploration, geological surveys, CT scans, and MRI are time-consuming, material-intensive, and expensive, and still lack intuitiveness. Some domestic and international scholars have used rocks and mortar blocks as similar materials to simulate the fracture evolution of rock masses, but the drawbacks are that the materials are opaque, making it impossible to directly observe the failure evolution process of the internal structure of the rock mass, and it is difficult to simulate real engineering conditions. Some scholars have also used plexiglass to simulate rock masses, but its physical properties differ greatly from most rock masses, making it unrepresentative, and it is impossible to embed simulated adverse geological bodies within it. Therefore, the current difficulties in studying the failure patterns of surrounding rock and lining structures lie in the inability to directly and clearly observe the effects of seepage channels and sudden water inrush on the internal structure, as well as the inability to effectively simulate, fabricate, and embed seepage channels and sudden water inrush cavities.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the background technology of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] In view of at least one of the above technical problems, this disclosure provides a rock-like specimen with pre-embedded seepage channels and / or sudden water inrush cavities and its preparation method. It mainly uses high-brittle resin to cast and mold simulate engineering rock mass, and solves the technical problem that existing simulation specimens cannot realistically simulate and intuitively observe the impact of seepage in seepage channels and / or sudden water inrush in water-rich cavities on the surrounding rock and lining structure inside the rock mass by burying tunnels and pre-embedded seepage channels and sudden water inrush cavities.

[0006] According to one aspect of this disclosure, a rock-like specimen with a pre-embedded seepage channel and / or sudden water inrush cavity is provided, comprising a rock-like mass cast from a highly brittle transparent resin to simulate an engineering rock mass, and a seepage channel, sudden water inrush cavity, or / or tunnel model embedded therein; the highly brittle transparent resin is composed of CY-39 epoxy resin and YS-T31 curing agent in a mass ratio of 100:34, and has good rock-like properties at -15 to -10°C; the seepage channel is a hollow structure formed by dissolving a soluble model body formed by 3D printing; the sudden water inrush cavity is a hollow model body formed by 3D printing; the tunnel model includes a 3D printed inner lining, a waterproof layer, and an outer lining, used to simulate a deep-buried mountain tunnel or a water conveyance tunnel.

[0007] In some embodiments of this disclosure, the soluble model body and / or the cavity model body are wrapped with thin white cotton rope of 1 mm diameter during installation to simulate the gradual transition of weak permeability between the tunnel and the intact rock mass. The average permeability coefficient of the cotton rope to water is 4.2 × 10 cm / s, the reference breaking force is 126 N, and it is insoluble in dilute acid. Specifically, a total of 39 turns of rope are wrapped around the surface of the gushing water cavity body, with a vertical distance of approximately 2 mm between each turn. Branches outside the printed seepage channel model are wrapped with rope every 4 mm. This simulates the gradual transition from geological defects to rock mass, making the experiment more realistic.

[0008] In some embodiments of this disclosure, the seepage channel is formed by dissolving a soluble model body printed in scale with chitosan in dilute acid; the gushing water cavity is a cavity model body printed in scale with polyvinyl chloride (PVC) as raw material. The surface of the printed model is rugged and protruding to be consistent with the real gushing water cavity in nature. After complete curing, a 0.2 mm water injection hole is opened on its top. After water is injected, it is sealed with resin. The preparation is completed after the resin is completely cured.

[0009] In some embodiments of this disclosure, the outer lining of the tunnel model is made of ABS plastic as the printing material, the waterproof layer is made of polyurethane rubber as the printing material, and the inner lining is made of ASA plastic as the printing material. After being 3D printed at a corresponding scale, the three are bonded and cured using silicone sealant.

[0010] The outer lining of the tunnel model is printed using ABS plastic as the printing material, the waterproof layer using polyurethane rubber as the printing material, and the inner lining using ASA plastic as the printing material. The inner lining, outer lining, and waterproof layer are constructed according to the formula... Calculate the corresponding scaling ratio for each, where, The relative stiffness similarity ratio between rock mass and structure; The similarity ratio of the elastic modulus of the rock mass; The similarity ratio of the tunnel outer diameter; The similarity ratio of the elastic modulus of the tunnel; The similarity ratio of lining thickness.

[0011] In some embodiments of this disclosure, the filling fluid in the surge water cavity and / or seepage channel has a density of 1.078 g / cm³. 3 The ethylene glycol liquid antifreeze is mixed with water at a volume ratio of 32:68, and when using it, 2g of water-soluble brilliant blue dye (C) is added to every 100ml of the mixed solution. 37 H 34 The mixture of N2Na2O9S3 and Na2O9S3 produces a medium blue liquid, allowing for a direct observation of the evolution of the effects of seepage and sudden water inrush on the internal structure.

[0012] According to another aspect of this disclosure, a method for preparing the above-mentioned rock-like specimen is provided, comprising the following steps:

[0013] (1) Preparation of resin casting material: Take CY-39 type epoxy resin and YS-T31 type curing agent, mix them evenly at a mass ratio of 100:34 and remove air bubbles in a vacuum machine;

[0014] (2) Preparation of seepage channel and sudden water cavity model: According to the corresponding size of the simulation specimen, the corresponding printing material is selected and soluble model body and cavity model body corresponding to seepage channel and sudden water cavity body are formed by 3D printing. Cotton rope is wrapped on it to simulate the gradual weak permeability process between the tunnel and the intact rock mass.

[0015] (3) Preparation of tunnel model: Based on the corresponding deep-buried mountain tunnel and water conveyance tunnel as prototypes, and based on the similarity ratio design, the inner lining, waterproof layer and outer lining of the tunnel model are 3D printed and bonded together in sequence.

[0016] (4) Embedding and casting of tunnels and seepage channels and / or sudden water inrush cavities: The tunnel model and seepage channels and / or sudden water inrush cavities are embedded in the corresponding positions of the resin parts by layer casting. After the three precast models are cast and embedded, the air bubbles are removed and the molds are dried and cured at 16-24℃ for 36-48 hours. When the mechanical strength of the cast specimen is ≥40 MPa, the specimens are demolded and then dried and cured at 75-80℃ for 48-60 hours.

[0017] In some embodiments of this disclosure, the soluble model body is 3D printed from chitosan with 98% purity, and after the resin is cast, a portion of the soluble model body embedded therein extends out of the specimen body so that the soluble model body can be dissolved with dilute hydrochloric acid to form corresponding seepage channels.

[0018] In some embodiments of this disclosure, the sudden water inrush cavity is a hollow mold made of polyvinyl chloride as raw material. After being filled with water through a pre-reserved water injection hole at the top, it is cured and sealed with the resin casting material and then embedded in a resin component to simulate a water-rich karst cave.

[0019] In some embodiments of this disclosure, in step (4), all three models are embedded in a layered casting manner. The tunnel model is pre-attached to the corresponding position of the mold with glue. When the seepage channel is cast, the first layer can be fixed after curing. When the sudden water cavity is cast, the second layer is cast 10mm away from the top of the sudden water cavity, which can fix the model. None of these will cause the pre-embedded structure to fall out of the fixed position after casting. Moreover, the timing of casting is strictly controlled. When the upper layer has just hardened and is sticky, the integrity of the specimen can be maintained.

[0020] In some embodiments of this disclosure, in step (4), the seepage channel model is positioned 3 mm in front of the tunnel face in the tunnel excavation direction, or / and the gushing water cavity model is positioned 2 mm in front of the tunnel face in the tunnel excavation direction.

[0021] One or more technical solutions provided in the embodiments of this application have at least one of the following technical effects or advantages:

[0022] 1. It can realistically simulate the structural characteristics of rock masses during tunnel excavation, as well as the seepage and sudden water inrush processes. Based on 3D printing, it can form various complex, winding seepage channel models of different sizes, which can better simulate the seepage channels that actually exist in natural rock masses. 3D printing can also form sudden water inrush cavities with uneven surfaces, which can better simulate the actual cavity shape inside natural rock masses. The tunnel model structure formed by 3D printing, consisting of an inner lining, a waterproof layer, and an outer lining, can better simulate the structure of deep-buried mountain tunnels or water conveyance tunnels. The brittleness index of the resin casting material after molding (i.e., the ratio of compressive strength to tensile strength of the specimen can reach 6.6 at a certain temperature) is more than twice that of the existing brittleness index of related transparent rock materials, which can more closely approximate the brittle characteristics of real rocks.

[0023] 2. The resin castable, seepage channels, sudden water inrush cavities, and / or tunnel models are highly transparent, allowing for clear and intuitive observation of the impact of seepage in the seepage channels and sudden water inrush in the water-rich cavities on the surrounding rock and lining structure inside the rock mass.

[0024] 3. The obtained rock specimens are transparent and easy to observe, can realize various working conditions, and have the characteristics of high brittleness of rocks. The evolution law of seepage and sudden water inrush under load can be clearly observed, and can be used for the study of seepage in the original seepage channel and the mechanism of sudden water inrush in the water-rich cavity. Attached Figure Description

[0025] Figure 1 This is a structural diagram of a 3D-printed adverse geological body in one embodiment of this application. In the diagram, (a) is a structural diagram of a seepage channel and (b) is a structural diagram of a sudden water inrush cavity.

[0026] Figure 2 In one embodiment of this application, the figure shows a casting material, (a) of which is CY-39 epoxy resin and YS-T31 curing agent, and (b) of which is a specimen sample obtained after casting, demolding and curing of the casting material.

[0027] Figure 3 This is a structural diagram of a tunnel in one embodiment of this application; in the diagram, a is an outer lining made of ABS plastic as the printing material, b is a waterproof layer made of rubber as the printing material, and c is an inner lining made of ASA plastic as the printing material.

[0028] Figure 4 This is a schematic diagram of the structure of a pre-cast specimen with a seepage channel model in one embodiment of this application.

[0029] Figure 5 This is a schematic diagram of the structure of a specimen cast with a pre-contained water inrush cavity model in one embodiment of this application.

[0030] Figure 6The figure shows the results of a fracturing test on a specimen with a seepage channel in one embodiment of this application. In the figure, 1 is a hollow crack; 2 is a thin line; 3 is a water injection pipe; 4 is a wrap-around wing crack; and 5 is a mottled crack. Detailed Implementation

[0031] To better understand the technical solution of this application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Unless otherwise specified, the components, structures, mechanisms, and other devices involved in the following embodiments are all commercially available products.

[0033] This example discloses a method for preparing a rock-like specimen pre-containing seepage channels and / or sudden water inrush cavities, mainly including the following steps:

[0034] 1. Preparation of Resin Castables

[0035] CY-39 epoxy resin and YS-T31 curing agent were mixed at a mass ratio of 100:34. After mixing, the mixture was placed in a vacuum chamber for 25 minutes to remove air bubbles, which was used to improve the molding quality of the specimens.

[0036] Ordinary resins generate a large amount of heat during curing. However, resins have poor thermal conductivity, leading to uneven heat dissipation and poor specimen molding results. This also affects the mechanical properties over time. If seepage channels, sudden water inrush cavities, or underground chambers are pre-embedded, molding becomes even more difficult. In contrast, the CY-39 epoxy resin and YS-T31 curing agent selected in this example generate almost no heat during the curing process, making them easy to mold and suitable for producing thicker specimens.

[0037] CY-39 epoxy resin and YS-T31 curing agent at a mass ratio of 100:34 can form highly transparent resin-based rock specimens (see...). Figure 2 It exhibits significant brittleness at -10 to -15°C, showing brittle fracture characteristics during compression testing, with a tensile-to-compression ratio reaching 6.6 / 1. The main mechanical parameters of the resin material of this invention at -15 to -10°C are shown in Table 1. In addition, Dyskin and Wong's experimental temperature was -50°C, and Song's experimental temperature was -20°C.

[0038] Table 1. Comparison of physical and mechanical parameters of resin materials, other transparent rock materials, and some real rocks in this example.

[0039] .

[0040] As can be seen from Table 1, the mechanical parameters of the new resin samples are close to those of real rocks, and therefore they can simulate these rocks to a certain extent.

[0041] 2. Preparation of the tunnel model

[0042] The tunnel model was scaled down proportionally based on the actual size of the tunnel and the dimensions of the mold, and then 3D modeled and printed. The outer lining thickness was 1mm, the waterproof layer thickness was 0.2mm, the inner lining thickness was 0.8mm, and the front end sealing thickness was 0.2mm. These components simulated the working face conditions and served only a supporting and shaping function within the model, without any mechanical significance. The 3D-printed tunnel model offers advantages such as high precision and a controllable manufacturing process, solving the problem of low precision in artificially prepared specimens for rock-related experiments. Furthermore, most existing similar specimens use through-tunnels, which can only simulate completed excavations. The tunnel proposed in this example can simulate geological defects such as seepage channels and sudden water inrush cavities that may exist ahead of the tunnel face in actual conditions. In addition, the inner lining, outer lining, and waterproof layer in the tunnel model were independently printed and then bonded together with adhesive of a certain strength after curing, allowing for a more realistic simulation of the corresponding working conditions in experiments. The mechanical parameters of the 3D printing material used to fabricate the tunnel are shown in Table 2.

[0043] Table 2 Physical properties of tunnel 3D printing materials

[0044] .

[0045] The horseshoe-shaped tunnel model was fabricated using fused deposition modeling (FDM) 3D printing technology. Specifically, ASA plastic was selected for 3D printing the tunnel outer lining, with a wall thickness of 1mm. The tunnel face was printed together with the outer lining, with a thickness of 0.2mm, serving only a molding function and having no mechanical significance. ABS plastic was selected for 3D printing the tunnel inner lining, with a wall thickness of 0.8mm. Polyurethane rubber was selected as the material for printing the tunnel waterproof layer, with a wall thickness of 0.2mm. After the three materials were printed separately, transparent silicone sealant was applied between the inner lining, outer lining, and waterproof layer. After dehydration and curing, the compressive and tensile strengths reached 68 and 60 MPa, respectively. The specimen was then cured at room temperature for 16 hours. The final overall tunnel model had a centerline height of 12mm and a bottom width of 8mm. (See also...) Figure 3 .

[0046] 3. Preparation of the seepage channel model

[0047] The principle behind the model preparation is to cast the printed model into the rock mass, and then dissolve it to form a hollow structure. Specifically, the seepage channel model uses 98% pure chitosan (C6H4O3). 11 NO4) nThe material is a white powder, which is sprayed and bonded by 3D printing technology. After the layered casting is completed, its top extends 2mm beyond the top of the cast specimen. Then, the specimen is sealed and soaked in a beaker for 8 hours with a sufficient amount of 5% dilute hydrochloric acid. The seepage channel model printed by chitosan is dissolved to simulate the seepage channel inside the rock mass.

[0048] The completed internal seepage channel model has an overall height of 182 mm, a width of 62 mm, and a length of 90 mm. It features numerous branches with varying cross-sectional sizes. Due to the high precision of 3D printing (0.1 mm), the smallest branch of the seepage channel has a diameter of 0.2 mm, effectively simulating the complex seepage geology and capillary seepage phenomena within natural rock masses. See also... Figure 1 (a).

[0049] 4. Preparation of the sudden water inrush cavity model

[0050] The water-rush cavity was constructed using 0.3mm thick polyvinyl chloride (PVC) as the raw material, appearing as a white powder. An STL model file was exported from 3D modeling software, scaled to the experimental scale, and then printed using a 3D printing process. The cavity wall thickness was 1mm. A 0.2mm diameter hole was pre-drilled at the top, and water was injected through a syringe to simulate a water-rich cavern. After water injection, the cavity was sealed using the same CY-39 resin and YS-T31 curing agent mixture used in this invention. It was then left to cure for 12 hours before being embedded in the specimen. The completed water-rush cavity specimen was approximately 80mm high, 64mm wide, and 74mm long, exhibiting a rugged surface. The deepest pits on the model surface reached 8mm from the outer surface. The 3D-printed water-rush cavity specimen showed relatively good uniformity and could simulate the shape of a real water-rich cavity in nature, demonstrating higher precision compared to artificially shaped cavity models. (See also...) Figure 1 (b).

[0051] The prepared seepage channels and gushing water cavities are permeable inside, while the resin-cast rock masses are impermeable. A 1mm diameter white fine cotton rope with permeability (the average permeability coefficient of the rope is 4.2×10cm / s, the reference breaking force is 126N, and it is insoluble in dilute hydrochloric acid) is wrapped around the prepared seepage channel and gushing water cavity models to simulate the transition process from permeable to impermeable. Specifically, a total of 39 turns of the rope are wrapped around the surface of the gushing water cavity, with a vertical distance of about 2mm between each turn. On the branches outside the printed seepage channel model, a turn of the rope is wrapped every 4mm. This effectively simulates the gradual transition process from geological defects to rock masses, making the experiment more realistic.

[0052] 5. Layout and positioning of tunnel, seepage channel, and sudden water inrush cavity model

[0053] (1) In the 3D modeling software, switch the front, back, left and right views of the specimen, capture and mark its coordinates on the four sides of the specimen, and draw the corresponding projection points on the four sides of the casting mold to achieve the effect of precise positioning; or adjust the placement of the adverse geological bodies in front in the 3D modeling software to achieve a variety of different working conditions.

[0054] (2) Based on the projection positioning points drawn on the side of the mold, first use strong adhesive to attach the tunnel to the organic polymer silicone mold to form a whole. Wait 15 minutes for the tunnel to be firmly attached before pouring resin. When performing the degassing process (because the tunnel and silicone mold form a closed space, degassing in the vacuum chamber will cause damage to the specimen), drill holes in the silicone mold to connect the interior of the underground cavern with the outside to prevent damage.

[0055] The seepage channel model is positioned directly in front of the tunnel excavation direction, 3mm ahead of the tunnel face (see...). Figure 4 The model of the sudden water inrush cavity is located directly in front of the tunnel excavation direction, 2mm ahead of the tunnel face (see...). Figure 5 ).

[0056] 6. Specimen casting

[0057] CY-39 epoxy resin and YS-T31 curing agent were mixed at a mass ratio of 100:34. After mixing, the mixture was placed in a vacuum chamber for 30 minutes to remove air bubbles and improve the molding quality of the specimens.

[0058] Place the fixed tunnel model in a high-polymer silicone mold on the worktable, and pour the prepared and processed mixture into the mold using a glass rod. After pouring, place the mold in a vacuum chamber again for 30 minutes to remove air bubbles, and then place it in an 18°C ​​constant temperature drying oven for 36 hours to complete the curing process.

[0059] The specimen with embedded seepage channels was cast in three stages. The bottom of the first layer was 120mm from the bottom of the mold's inner side, so the first layer was 120mm high. After a 60-minute interval, the resin pre-cured, and the seepage channel model was placed in the mold. The second layer was then cast to a height of 90mm. After 45 minutes, the second layer pre-cured, fixing the lower half of the model. Finally, the third layer was cast to a height of 90mm. The specimen with embedded burst water cavities was cast in three stages. The bottom of the first layer was 110mm from the bottom of the mold's inner side, so the first layer was 110mm high. After a 60-minute interval, the cavity model was placed in the mold. The second layer was cast to a height of 40mm. After a 30-minute interval, the resin pre-cured, fixing the lower half of the model. Finally, the third layer was cast to a height of 150mm. During these intervals, the viscosity of the resin casting material increased, preventing the embedded structural model from sinking and maintaining the specimen's integrity.

[0060] 7. Demolding and curing

[0061] Once the specimen has achieved a mechanical strength greater than 40 MPa, remove the mold, ensuring the appearance of the specimen remains undamaged during demolding. Place the demolded specimen in a constant-temperature drying oven at 75℃ for 48 hours to cure, thus completing the specimen fabrication.

[0062] Example 2: Experimental Verification

[0063] 1. Preparation of simulated fractured rock mass specimens

[0064] (1) Fabrication and layout of tunnel, seepage channel and sudden water inrush cavity model

[0065] The specimen was fabricated using the 3D printing technology described in Example 1. The tunnel model's opening was positioned at the center of the specimen's side, with both the left and right sides 71 mm from the specimen's edge. The seepage channel was positioned 3 mm in front of the tunnel face, extending 2 mm beyond the specimen at the top and 120 mm from the bottom of the specimen. The sudden water inrush cavity was positioned 2 mm in front of the tunnel face, with the top and bottom of the model 110 mm from the upper and lower surfaces of the specimen, respectively.

[0066] (2) Arrangement and fixation of water-filled and non-water-filled fissures

[0067] In the 3D modeling software, switch between the front, back, left, and right views of the specimen, capture and label its coordinates on the four sides of the specimen, draw the corresponding projection points on the four sides of the casting mold, and then cast it into the specimen in layers.

[0068] (3) Specimen casting

[0069] CY-39 resin and YS-T31 modified amine curing agent were mixed at a mass ratio of 100:34. After mixing, the mixture was placed in a vacuum chamber for 30 minutes to remove air bubbles and improve the molding quality of the specimens.

[0070] Place the fixed tunnel-shaped polymer silicone mold on the workbench, and use a glass rod to guide the prepared and processed mixture into the mold in steps for casting. After casting, place the mold back into the vacuum chamber for degassing treatment for 30 minutes, and then place it in a 18℃ constant temperature forced air drying oven for 36 hours to complete the curing process.

[0071] (5) Demolding and curing

[0072] Once the specimen has achieved a mechanical strength of 40 MPa, remove the mold, ensuring the appearance of the specimen remains undamaged during demolding. Place the demolded specimen in a 75℃ constant temperature forced-air drying oven for 36 hours to complete specimen fabrication.

[0073] 2. Water injection fracturing test

[0074] The experimental equipment mainly consisted of a water injection system and a uniaxial compression device. The water injection system was able to maintain a constant water pressure. Before the test, the specimens had to be stored in a refrigerator at -20°C for 24 hours to ensure that the specimens possessed the rock-like brittleness required for the experiment. During the experiment, dry ice was placed around the specimens to maintain low-temperature conditions (within the range of -15°C to -10°C), and an infrared thermometer was used to monitor temperature changes. The fracturing fluid was a solution of transparent ethylene glycol liquid antifreeze with a density of 1.078 g / cm³ mixed with water, and was colored with a dye.

[0075] The specimen containing the inrush water cavity was subjected to a fracturing test under uniaxial compression. When water permeated the boundary of the surrounding rock, the initial seepage field was a non-static field. The specimen developed cracks when the axial force was 48.7 MPa. With continued pressurization, the inrush water cavity entered the inrush water stage when the axial force was 53.6 MPa, and entered the high inrush water stage when the axial force was 63.5 MPa, and then entered the decay stage.

[0076] The specimens containing pre-existing seepage channels were subjected to fracturing tests under uniaxial compression with an internal water pressure of 2 MPa. The test results are shown in Table 3 and... Figure 6 As shown, water pressure was slowly applied to a predetermined level. During the steady increase of water pressure to the predetermined value, no specimens cracked. After the water pressure reached the predetermined value, a pressure-maintaining system was used to stabilize the water pressure, and then axial loading was continued on the specimens. When the axial stress increased to a certain value, seepage cracks began to develop, and the seepage rate changed. This was due to the effect of water pressure, which caused deformation and displacement of the cracks and surrounding materials, eventually leading to stability. With the continuous increase of axial force, transverse seepage cracks gradually developed to the tunnel lining and the sides of the specimens.

[0077] Table 3. Development and Penetration Stress of Seepage Fractures under Three Types of Internal Water Pressure

[0078] Water pressure / MPa Crack propagation stress / MPa Lateral crack penetration stress / MPa 0 36.3 61.5 4 9.1 16.4 6 3.5 9.6

[0079] Although some preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0080] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the inventive spirit and scope of this application. Therefore, if such modifications and variations to this application fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A rock-like test specimen pre-buried with seepage passage and / or sudden-inrush cavity, characterized in that, Including rock-like masses cast from highly brittle transparent resin to simulate engineering rock masses, as well as tunnel models and seepage channels and / or sudden water inrush cavities embedded within them; The highly brittle transparent resin is a mixture of CY-39 epoxy resin and YS-T31 curing agent at a mass ratio of 100:34, and it exhibits good rock-like properties at -15 to -10℃. The seepage channel is a hollow structure formed by dissolving a soluble model body printed by 3D printing. The sudden water inrush cavity is a hollow model body printed by 3D printing. The tunnel model includes a 3D printed inner lining, a waterproof layer, and an outer lining, used to simulate a deep-buried mountain tunnel or a water conveyance tunnel. The soluble model body and / or the cavity model body are wrapped with a 1mm diameter white thin cotton rope around them during installation to simulate the gradual weak permeability process between the tunnel and the intact rock mass; the average permeability coefficient of the cotton rope to water is 4.2×10cm / s, the reference breaking force is 126N, and it is insoluble in dilute acid. The seepage channel is formed by dissolving a soluble model body printed in scale with chitosan in dilute acid; the gushing water cavity is a hollow model body printed in scale with polyvinyl chloride as the raw material.

2. The rock-like test piece according to claim 1, characterized by The outer lining of the tunnel model is printed using ABS plastic as the printing material, the waterproof layer using polyurethane rubber as the printing material, and the inner lining using ASA plastic as the printing material. The inner lining, outer lining, and waterproof layer are constructed according to the formula... Calculate the corresponding scaling ratio for each, where, The relative stiffness similarity ratio between rock mass and structure; The similarity ratio of the elastic modulus of the rock mass; The similarity ratio of the tunnel outer diameter; The similarity ratio of the elastic modulus of the tunnel; The similarity ratio of the lining thickness.

3. The rock-like test piece according to claim 1, characterized by The filling liquid in the sudden gushing water cavity or / and seepage passage is mixed by ethylene glycol liquid antifreeze with density 1.078 g / cm 3 3 and water according to the volume ratio of 32:68, and 2 g of water-soluble bright blue dyeing agent is added in every 100 ml of the mixed solution during use.

4. The method of claim 1, wherein the rock-like specimen is prepared by the steps of: Includes the following steps: (1) Preparation of resin casting material: Take CY-39 type epoxy resin and YS-T31 type curing agent, mix them evenly at a mass ratio of 100:34 and remove air bubbles in a vacuum machine; (2) Preparation of seepage channel and sudden water cavity model: According to the corresponding size of the simulation specimen, the corresponding printing material is selected and soluble model body and cavity model body corresponding to seepage channel and sudden water cavity body are formed by 3D printing. Cotton rope is wrapped on it to simulate the gradual weak permeability process between the tunnel and the intact rock mass. (3) Preparation of tunnel model: Based on the corresponding deep-buried mountain tunnel and water conveyance tunnel as prototypes, and based on the similarity ratio design, the inner lining, waterproof layer and outer lining of the tunnel model are 3D printed and bonded together in sequence. (4) Installation and casting of tunnels and seepage channels and / or sudden water inrush cavities: The tunnel model and seepage channels and / or sudden water inrush cavities are installed in the corresponding positions of the resin parts by layered casting and then cured.

5. The preparation method according to claim 4, characterized in that, The soluble model body is 3D printed using chitosan with 98% purity as raw material. After the resin is poured, a portion of the soluble model body embedded in it extends out of the specimen body so that it can be dissolved with dilute hydrochloric acid to form corresponding seepage channels.

6. The preparation method according to claim 4, characterized in that, The water-rush cavity is a hollow mold made of polyvinyl chloride. After being filled with water through a pre-reserved water injection hole at the top, it is cured and sealed with the resin casting material and then embedded in a resin component to simulate a water-rich karst cave.

7. The preparation method according to claim 4, characterized in that, In step (4), the seepage channel and / or the sudden water inrush cavity are buried in three stages. When the first layer of burying reaches the height of the model, the burying material is allowed to solidify for a certain period of time before the corresponding seepage channel model is placed to prevent it from sinking. When the second layer of burying reaches half the height of the model, the second layer is allowed to solidify for a certain period of time to fix the lower half of the seepage channel model, thereby achieving accurate positioning of the model. Finally, the third layer of burying reaches the design height of the specimen.

8. The preparation method according to claim 4, characterized in that, In step (4), the seepage channel model is located 3 mm in front of the tunnel face in the tunnel excavation direction, or / and the sudden water inrush cavity model is located 2 mm in front of the tunnel face in the tunnel excavation direction.

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