An experimental device and method for testing the plugging and impact resistance of grouting materials

Abstract

The application discloses an experimental device and method for testing the plugging and impact resistance of grouting materials, and adopts a simple "pipeline and piston" core structure. The device has the advantages of simple structure, convenient operation, easy disassembly and reusability, and controllable cost, thereby meeting the needs of efficient and batch testing. The device is provided with a piston push-pull rod with a scale mark and is equipped with a locking mechanism capable of locking the piston push-pull rod. The device realizes external visualization, quantitative and accurate adjustment and fixation of the plugging length, guarantees the consistency of the specimen length in each experiment, and significantly improves the parallelism and accuracy of the data. The device is provided with roughness simulation structures on the inner wall of the pressure testing pipeline, such as processing grooves and setting replaceable rough inner liners. The slurry is in-situ formed and tested in the simulated rough pipeline wall, the "mechanical engagement" effect between the slurry and the rock wall is truly restored, and the data of the anti-erosion performance more in line with the actual geological conditions are obtained.

Description

Technical Field

[0001] This invention relates to the field of civil engineering material testing and grouting simulation technology, and in particular to an experimental apparatus and method for testing the sealing and impact resistance performance of grouting materials. Background Technology

[0002] Currently, in the treatment of sudden water inrushes in tunnels, mines, and underground engineering projects, non-aqueous reactive expandable polymer materials are widely used in dynamic water grouting and sealing projects due to their rapid reaction, high expansion ratio, and strong impermeability. To verify the sealing effect of the materials, researchers and engineers usually need to conduct indoor simulation experiments.

[0003] Existing simulation experimental devices are mainly divided into two categories:

[0004] Large-scale physical model test benches: Currently disclosed patents include large-scale high-pressure water simulation systems. While these devices simulate realistic environments, they are difficult to mass-produce. Existing high-pressure water grouting and sealing indoor simulation devices typically consist of large pressurized water tanks, flange sealing systems, and external high-pressure pump stations, resulting in a bulky and expensive overall structure. Such devices require cumbersome sealing assembly during the experimental preparation phase, and the disassembly and cleaning of the molds after the grouting material has cured are extremely time-consuming and labor-intensive. This leads to excessively long experimental cycles, making it difficult to meet the needs of scientific research and engineering testing for rapid, low-cost, and mass comparative testing of multiple variables. Consequently, researchers often only obtain a very small number of data points, lacking statistical significance, making it difficult to establish reliable probabilistic failure models.

[0005] Simplified Transparent Tube Model: Currently, transparent acrylic tubes are commonly used in laboratories for direct grouting observation. However, in actual operation, there is a lack of precise control over the forming length of the sealing body, resulting in large dispersion of experimental data. Due to the rapid reaction and high volume expansion ratio of expandable polymers, existing simplified pipe models lack internal limiting mechanisms that can be precisely adjusted externally, leading to a "non-visualized" grouting process. Experimenters cannot accurately control the expansion boundary and final forming length of the material within the pipe, causing inconsistent sealing lengths among specimens in the same batch of experiments. This severely affects the parallelism and accuracy of impact resistance test data, making it difficult to establish quantitative patterns for analysis.

[0006] Existing technologies also have the following shortcomings: the inner wall of the pipe is too smooth, making it impossible to realistically simulate the rough characteristics of the surrounding rock surface. Current simulation experiments often use acrylic, PVC, or smooth steel pipes, whose inner wall friction coefficient is far lower than that of tunnel fissures or rock surfaces in actual engineering projects. This smooth interface cannot replicate the anti-slip effect generated by the "mechanical interlocking force" between the polymer material and the surrounding rock, resulting in the critical failure pressure measured in experiments often being lower than the actual working condition value. This distorts the experimental environment and fails to objectively reflect the material's true sealing performance under complex geological conditions.

[0007] Linear simplification error in mechanical models: Current engineering designs mainly use simplified linear friction models, assuming that the shear stress at the interface between the grout and the rock mass is uniformly distributed along the axial direction. However, according to the shear hysteresis theory, under the thrust of high-pressure water, the interfacial shear stress actually decreases nonlinearly exponentially from the stressed end to the distal end, resulting in significant stress concentration. This linear assumption leads to two serious misjudgments in engineering practice: 1. Overestimation of the effectiveness of long-distance sealing: The linear model mistakenly assumes that the erosion resistance P will increase linearly and infinitely with the increase of the sealing length L. In reality, when the length exceeds the "effective sealing length," the grouting material at the distal end hardly bears any shear force. This means that designers may mistakenly believe that increasing the grouting length can resist higher water pressure, but in fact, the added length does not play a role, resulting in the actual anti-slip capacity being far lower than the design expectation, which can easily lead to water inrush accidents. 2. Waste of materials and construction time: Due to the inability to identify the effective stress transmission depth, excessively long grouting sections (such as several meters or even tens of meters) are often blindly used in engineering, when in fact only a shorter initial section may be needed to achieve the same bearing capacity. This blindly extended design resulted in a huge waste of grouting materials and an unnecessary extension of the construction period.

[0008] Therefore, there is an urgent need for a new type of device with a simple structure, capable of accurately controlling the internal sealing distance through external scales, and easy to simulate water flow impact conditions, as well as related calculation methods that consider shear hysteresis effects. Summary of the Invention

[0009] The purpose of this invention is to provide an experimental apparatus and method for testing the sealing and impact resistance properties of grouting materials, thereby solving the technical problems existing in the background art.

[0010] This invention is achieved by providing an experimental apparatus for testing the sealing and impact resistance properties of grouting materials, the apparatus comprising:

[0011] The pressure testing pipe is open at both ends to accommodate grouting material and withstand fluid pressure; the inner wall of the pipe has a roughened structure to simulate the wall of a real soil pore.

[0012] A piston structure, comprising a piston head and a push-pull rod, wherein the piston head is located inside the pressure test pipe and its outer diameter is adapted to the inner diameter of the pressure test pipe, one end of the push-pull rod is connected to the piston head and the other end extends to the outside of the pressure test pipe, and the push-pull rod is provided with scale markings.

[0013] A locking mechanism is provided to lock the push-pull rod relative to the pressure test pipe to fix the axial position of the piston head within the pressure test pipe.

[0014] By integrating a graduated push-pull rod and a locking mechanism, precise external control and fixation of the sealing length are achieved within an opaque pipe, fundamentally solving the problem of controlling the forming length of the sealing body. Simultaneously, the roughened structure of the pipe's inner wall simulates a real rock wall, making the testing conditions closer to actual engineering conditions. The entire device has a simple structure, is easy to operate, and can be reused. The locking mechanism can withstand fluid impact to achieve rigid locking of the push-pull rod and the pressure testing pipe, and ensures that the slurry forms in its original position and is tested in situ during use.

[0015] A further technical solution of the present invention is that the roughened structure is at least one of the following: grooves, knurling textures, sandblasted rough surfaces, or chemically etched surfaces processed on the inner wall of the pressure test pipe.

[0016] It provides a specific and reliable implementation plan for roughening the inner wall of the pipe, which can effectively simulate the rough undulation of the surface of rock fractures, so as to generate real mechanical interlocking and frictional resistance between the grout and the pipe wall, thereby obtaining more accurate anti-slip performance data.

[0017] A further technical solution of the present invention is: the roughened structure is a replaceable inner liner installed inside the pressure test pipe, and the inner surface of the inner liner is pre-formed with a rough texture.

[0018] The replaceable inner liner design allows a single device to quickly switch between different roughness conditions, greatly expanding the flexibility and efficiency of testing. At the same time, after an experiment, only the inner liner needs to be replaced to quickly conduct the next set of tests, solving the problems of difficult cleaning and long experimental cycles of traditional devices.

[0019] A further technical solution of the present invention is: the locking mechanism includes a positioning cover and a locking member. The positioning cover is detachably installed at one end of the pressure test pipe. The positioning cover is provided with a central through hole for the push-pull rod to pass through. The locking member is provided on the positioning cover for pressing and fixing the push-pull rod after it passes through the central through hole.

[0020] A simple and easy-to-operate locking scheme is provided, which can reliably resist the huge thrust generated when the grouting material expands, ensuring that the piston position does not shift during the grouting curing process, thereby ensuring the accuracy and consistency of the sealing body length.

[0021] A further technical solution of the present invention is that the positioning cover is installed on the pressure test pipeline by means of thread or flange connection.

[0022] It adopts mature and reliable connection methods such as threads or flanges, which ensure the sealing performance of the positioning cover installation and the reliability of bearing high pressure, while facilitating quick disassembly and assembly, meeting the needs of batch and efficient testing.

[0023] A further technical solution of the present invention is that the piston head is provided with at least one sealing ring on its outer periphery.

[0024] By setting a sealing ring, leakage of uncured grout from the gap between the piston head and the pipe wall is effectively prevented. This not only ensures the airtightness of the grouting chamber to accurately control the volume of the sealing body, but also avoids interference with the experimental environment and data accuracy caused by leakage.

[0025] A further technical solution of the present invention is: one end of the pressure test pipe is provided with a grouting port, and the other end is provided with a connection interface for connecting a high-pressure fluid source, wherein the connection interface is provided with threads on its outer periphery.

[0026] The grouting and loading function interfaces of the device were clearly defined, making it a complete testing system. The threaded connection interface facilitates quick and sealed connection with standard high-pressure pipelines, achieving a seamless transition from sample preparation to hydrostatic impact testing.

[0027] The present invention also provides a method for testing the sealing and impact resistance properties of grouting materials, using the aforementioned experimental apparatus, and the method includes the following steps:

[0028] S1: Inside the pressure test pipeline, by adjusting and locking the position of the piston head, a grouting material sealing body with a specific length L is prepared;

[0029] S2: After removing the piston structure, apply fluid pressure to the plug until it is destroyed, and record the critical destruction pressure P;

[0030] S3: Change the position of the piston head and repeat steps S1 and S2 at least three times to obtain multiple sets of measured data pairs of different sealing lengths L and their corresponding critical failure pressures P.

[0031] S4: Based on the shear hysteresis theory, a nonlinear constitutive equation is established between the critical failure pressure P and the sealing length L. The nonlinear constitutive equation is as follows:

[0032]

[0033] Critical failure pressure (measured value, MPa);

[0034] : Blocking length (independent variable, precisely controlled by the device, in meters);

[0035] Pipe inner diameter (constant, m);

[0036] Peak bond strength; characterizes the chemical bonding and mechanical interlocking ability of a material, and determines whether initial loosening occurs;

[0037] Residual bond strength; characterizes the sliding friction resistance after interface failure and determines the anti-slip capability after failure;

[0038] Stress transmission attenuation coefficient; characterizing the rate of attenuation of hydrodynamic thrust along the interface. It is the core indicator for calculating the effective blocking length.

[0039] S5: Substitute the multiple sets of measured data obtained in step S3 into the nonlinear constitutive equation, perform fitting analysis, and invert to obtain... .

[0040] This method combines precise and controllable physical experiments with scientific mechanical models. By obtaining key data through variable-length experiments and then using a model based on shear hysteresis theory for inversion, it can quantitatively characterize the peak strength, residual strength, and stress decay characteristics of materials under simulated real rough interfaces, fundamentally overcoming the shortcomings of traditional linear models, such as large errors and inability to reflect size effects.

[0041] A further technical solution of the present invention is: substituting the multiple sets of measured data obtained in step S3 into the nonlinear constitutive equation, performing nonlinear regression analysis using the least squares method, and inverting to calculate the three key mechanical parameters of the grouting material under the current geological model: .

[0042] The use of least squares for parameter inversion was clarified. This is a standard and reliable mathematical tool that can efficiently and accurately extract constitutive parameters from experimental data, ensuring the scientific validity and repeatability of the evaluation results.

[0043] A further technical solution of the present invention is: in step S1, by observing the scale markings set on the push-pull rod fixedly connected to the piston structure, the axial position of the piston structure in the pressure test pipe can be visually adjusted and determined from the outside of the pressure test pipe.

[0044] The study emphasizes the importance of precise control using the device's visual scale, a crucial step in achieving the core premise of "variable length" sample preparation. This ensures that the plugging length L for each experiment is known and accurate, laying a solid foundation for establishing reliable PL data relationships and accurate parameter inversion.

[0045] The beneficial effects of this invention are as follows: Large-scale high-pressure model devices are complex in structure and cumbersome to assemble and disassemble, resulting in long experimental cycles and making batch comparative testing difficult. This invention adopts a simplified "pipe-piston" core structure. The device structure is simplified, operation is easy, it is easy to disassemble and reuse, and the cost is controllable, thus meeting the needs of efficient, batch testing.

[0046] Existing devices lack internal limit adjustment mechanisms, and the grouting process is "invisible," leading to inaccurate control of the sealing body's forming length and discrepancies in experimental data. This invention addresses this issue by providing a piston push-pull rod with graduated markings and a locking mechanism (such as a positioning cap and locking screw) to lock it in place. This achieves external visualization, quantitative, and precise adjustment and fixation of the sealing length, ensuring consistent specimen length in each experiment and significantly improving data parallelism and accuracy.

[0047] The problem stems from the fact that the inner wall of the experimental pipe is too smooth to simulate the rough surface of real rock, leading to discrepancies between the measured anti-slip performance and actual engineering conditions. This invention addresses this by designing a roughness simulation structure on the inner wall of the pressure testing pipe, such as machining grooves and installing replaceable rough linings. The slurry is formed and tested in situ within the simulated rough pipe wall, realistically replicating the "mechanical interlocking" effect between the slurry and the rock wall, thereby obtaining erosion resistance data that more closely reflects actual geological conditions.

[0048] Existing evaluation methods employ simplified linear friction models that neglect the "shear hysteresis effect" under high pressure, failing to accurately explain the nonlinear decay law of plugging efficiency. This invention introduces shear hysteresis theory into the evaluation system, establishing a nonlinear plugging strength model that includes peak strength, residual strength, and decay coefficient, and performing parameter inversion using variable-length experiments. The proposed nonlinear model corrects the errors of traditional linear formulas, and by decoupling peak strength and residual strength, it can more scientifically and accurately evaluate the plugging performance and failure mechanism of materials. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the pressure testing pipeline provided by the present invention;

[0050] Figure 2 This is a schematic diagram of the piston structure provided by the present invention;

[0051] Figure 3 This is a schematic diagram of the locking mechanism provided by the present invention;

[0052] Figure 4 This is an exploded view of the structure provided by the present invention;

[0053] Figure 5 This is a schematic diagram of the connection between the high-pressure water injection device and the pressure testing pipeline provided by the present invention;

[0054] Figure 6 This is a flowchart of the testing method provided by the present invention.

[0055] Attached reference numerals: 1. Connection interface, 2. Grouting port, 3. Pressure test pipe, 4. Handle, 5. Push-pull rod, 6. Piston head, 7. Sealing ring, 8. Positioning cover, 9. Central through hole, 10. Locking element, 11. Water storage tank, 12. Pressurizing equipment, 13. Pressure gauge, 14. Straight-through ball valve. Detailed Implementation

[0056] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0057] Example 1:

[0058] like Figure 1-5 The diagram shows an experimental apparatus for testing the sealing and impact resistance properties of grouting materials. The apparatus includes...

[0059] The pressure test pipe 3 is open at both ends to accommodate grouting material and withstand fluid pressure; the inner wall of pipe 3 has a roughened structure to simulate the wall of a real rock and soil pore.

[0060] The piston structure includes a piston head 6 and a push-pull rod 5. The piston head 6 is located inside the pressure test pipe 3 and its outer diameter is adapted to the inner diameter of the pressure test pipe 3. One end of the push-pull rod 5 is connected to the piston head 6 and the other end extends to the outside of the pressure test pipe 3. The push-pull rod 5 is provided with scale markings.

[0061] A locking mechanism is provided to lock the push-pull rod 5 relative to the pressure test pipe 3 to fix the axial position of the piston head 6 within the pressure test pipe 3.

[0062] In this embodiment, an axially movable piston is provided inside the pressure test pipe 3; the piston is connected to a push-pull rod 5 extending to the outside of the pipe; and the push-pull rod 5 is provided with scale markings to indicate the position of the piston inside the pipe, thereby limiting the sealing length of the grouting material.

[0063] In this embodiment, a locking mechanism is provided on the push-pull rod 5. During the reaction of the expanding polymer, the pressure is very high; without locking, the piston will be pushed away, and the scale will become ineffective. This is a crucial supplementary structure for achieving precise control.

[0064] In this embodiment, the sealing structure includes a sealing ring 7 around the piston. This prevents the slurry from leaking out of the piston gap before it solidifies, thus affecting the accuracy of the sealing length.

[0065] In this embodiment, a simulated water pressure system is used: one end of the pipe is connected to a water storage tank 11, and the outlet end of the pipe, i.e., the connection interface 1, is connected to a pressurizing device 12. This demonstrates that the device possesses the function of simulating water impact, making it not merely a grouting mold, but a complete testing system.

[0066] In this embodiment, the pressure testing pipeline 3 is a thick-walled, high-pressure metal pipeline open at both ends. The inner wall of the pipeline has a roughened structure, such as machined annular grooves, spiral grooves, or an internal sandblasted rough surface, to simulate the borehole wall of a real rock and soil drill hole. Both ends are equipped with high-pressure connection structures, which are high-pressure flanges or high-strength threads.

[0067] In this embodiment, the removable piston structure serves as a temporary baffle during grouting and a cavity generator after molding. It includes...

[0068] Piston head 6: Its outer diameter is precisely matched with the inner diameter of the pipe.

[0069] Sealing ring 7: At least 1 to 2 rings are provided on the outer circumference of piston head 6. The material is nitrile rubber. It is used to seal during grouting to prevent grout leakage.

[0070] Push-pull rod 5: A rigid metal rod, one end of which is firmly connected to the piston head 6, and the other end, i.e. the hand-held end, extends out of the pipe.

[0071] Scale: The push-pull rod 5 is equipped with a length scale, with each scale mark being 1 cm, which is used to accurately position the piston head 6, thereby quantitatively controlling the grouting length.

[0072] In this embodiment, the locking mechanism includes:

[0073] Positioning cap 8: A threaded cap that can seal the water outlet.

[0074] Center through hole 9: There is a smooth, precise round hole in the center of the positioning cover 8. The diameter of this hole is just right to allow the push-pull rod 5 to pass through freely and smoothly, but without too much wobbling.

[0075] Locking element 10: namely, the lateral locking screw, which has a threaded hole perpendicular to the central through hole 9 on the side of the positioning cover 8. A locking screw is screwed into this lateral hole. When this locking screw is tightened, its tip will push laterally and forcefully against the side of the push-pull rod 5 that passes through the central hole 9.

[0076] In this embodiment, the specific implementation scheme for the roughening of the pipe is designed based on the following: In actual underground engineering, the roughness and undulation of the rock mass fracture surface (i.e., the JRC joint roughness coefficient) is a key factor determining the bonding strength between the grout and the surrounding rock. Existing smooth pipes (JRC≈0) cannot simulate the mechanical interlocking effect formed when grout fills the uneven surface of the rock wall. It can be understood that the roughness and undulation of the actual rock mass fracture surface is a key factor affecting the shear strength of the "polymer-rock" interface. During the expansion process, the polymer fills the tiny depressions in the rock wall, forming a mechanical interlocking structure similar to a pin after solidification.

[0077] Low roughness group (JRC 0-5): Simulates straight joints or polished rock walls;

[0078] Medium roughness group (JRC 5-10): simulates typical natural tensile fractures;

[0079] High Roughness Group (JRC 10-20): Simulates rock surfaces with severe undulations caused by shearing or fracturing.

[0080] This invention prefabricates the inner wall of the pipe with the aforementioned specific JRC value undulation, such as through 3D printing of the inner lining, CNC grooving, or inner wall casting process. This allows the grouting-formed sealing body to generate real frictional resistance and interlocking force with the pipe wall, thereby obtaining critical pressure data for water flow impact that is more consistent with engineering practice.

[0081] As another embodiment, standardized trench simulation:

[0082] Rock roughness: To standardize experimental conditions, this invention uses regular geometric grooves to simulate the shear resistance of natural rocks. In the experimental system of this invention, the low roughness group consists of shallow microgrooves with a processing depth h = 0.5 mm. Mechanism description: At this depth, the slurry and the pipe wall mainly generate sliding friction resistance, simulating a relatively smooth rock joint surface with only minor undulations.

[0083] Medium roughness group: Standard grooves with a machining depth h = 1.0 mm. Mechanism description: At this depth, the slurry begins to form obvious shear bonds, with friction and mechanical interlocking coexisting, simulating natural tensile fractures with a certain degree of undulation.

[0084] High roughness group: Deep grooves with a machining depth of h=2.0mm. Mechanism description: At this depth, the grout forms a stable structure within the groove, mainly resisting shear through mechanical interlocking, simulating the surface of rock masses with severe undulations or shearing fractures.

[0085] This simplified approach enables repeatable experimental boundary conditions for complex geotechnical problems. By changing the geometric parameters of the trench, the influence of borehole wall roughness on sealing performance can be quantitatively studied.

[0086] As another embodiment, a replaceable inner liner can be used to simulate:

[0087] To further improve the versatility and service life of the device, a replaceable inner liner structure is also designed. The inner liner is a thin-walled cylinder whose outer diameter matches the inner diameter of the pressure test pipe 3. During installation, it is pushed into the pipe and its axial position is limited and fixed by the end caps (grouting caps, positioning caps 8) at both ends of the pipe.

[0088] Functional advantages: The inner surface of the liner has a pre-formed rough texture (which can be made through 3D printing or inner wall spraying). After the experiment, simply remove the old liner and replace it with a new one to quickly proceed to the next set of experiments, without the need to clean or rework the heavy metal pipe body.

[0089] It should be noted that although the above embodiments describe the roughening structure using trapezoidal threads and 3D-printed bushings as examples, those skilled in the art should understand that any structural form that can increase the surface roughness of the inner wall of the pipe, improve the mechanical interlocking force or frictional resistance between the grouting stone and the pipe wall, is covered within the scope of protection of this invention. Specific alternative forms include, but are not limited to: machining: rectangular threads, sawtooth threads, knurled textures; physical and chemical treatment: sandblasted surfaces, acid-etched rough surfaces, laser-etched textures; adhesive coatings: inner wall adhesive quartz sand coating, epoxy resin particle layer; shaped pipes: directly using shaped steel pipes with raised ribs on the inner wall. These simple substitutions or modifications based on the technical concept of this invention do not depart from the technical scope of this invention.

[0090] The assembly method of the experimental device is as follows: Insert the removable piston structure into the connection interface 1 of the pressure test pipe 3. At this time, the handle 4 of the removable piston structure is inserted into the central through hole 9, and the positioning cover 8 is installed on the high-strength thread of the connection interface 1; slide the push-pull rod 5 and observe the scale on the rod until the piston head 6 reaches the desired depth (e.g., 15cm); tighten the locking screw 10 on the side of the cover plate. This screw will firmly hold the push-pull rod 5, making it unable to move; inject the polymer material through the grouting port 2; once the material slurry has successfully shaped, immediately pull out the piston, remove the removable piston structure and the positioning cover 8; wait for the slurry to completely solidify and form; connect the test pipe to the high-pressure water injection device.

[0091] The high-pressure water injection device includes a water storage tank 11, a pressurizing device 12 and a pressurizing pipeline connected in sequence. A pressure gauge 13 is installed on the pressurizing pipeline, and the pressurizing pipeline is connected to the pressure test pipeline 3 through a straight ball valve 14.

[0092] Example 2:

[0093] like Figure 1-6 The method for testing the sealing and impact resistance of grouting materials is characterized by using the experimental apparatus described in Example 1, and the method includes the following steps:

[0094] S1: Inside the pressure test pipe 3, by adjusting and locking the position of the piston head 6, a grouting material sealing body with a specific length L is prepared;

[0095] S2: After removing the piston structure, apply fluid pressure to the plug until it is destroyed, and record the critical destruction pressure P;

[0096] S3: Change the position of the piston head 6, repeat steps S1 and S2 at least three times, and obtain multiple sets of measured data pairs of different sealing lengths L and their corresponding critical failure pressures P;

[0097] S4: Based on the shear hysteresis theory, a nonlinear constitutive equation is established between the critical failure pressure P and the sealing length L. The nonlinear constitutive equation is as follows:

[0098]

[0099] Critical failure pressure (measured value, MPa);

[0100] : Blocking length (independent variable, precisely controlled by the device, in meters);

[0101] Pipe inner diameter (constant, m);

[0102] Peak bond strength; characterizes the chemical bonding and mechanical interlocking ability of a material, and determines whether initial loosening occurs;

[0103] Residual bond strength; characterizes the sliding friction resistance after interface failure and determines the anti-slip capability after failure;

[0104] Stress transmission attenuation coefficient; characterizing the rate of attenuation of hydrodynamic thrust along the interface. It is the core indicator for calculating the effective blocking length.

[0105] S5: Substitute the multiple sets of measured data obtained in step S3 into the nonlinear constitutive equation, perform fitting analysis, and invert to obtain... .

[0106] In this embodiment, multiple sets of grouting and sealing bodies of different lengths (L) are prepared in situ within a channel with a constant inner wall roughness by changing the position of the molding boundary.

[0107] In this embodiment, fluid pressure is applied to each group of plugs until they are destroyed, and the critical destruction pressure (P) is recorded.

[0108] In this embodiment, based on the shear hysteresis mechanism, a nonlinear constitutive equation is constructed that includes peak bond strength, residual bond strength, and attenuation coefficient:

[0109] In this embodiment, the measured PL data is substituted into the equation for regression analysis to obtain the material parameters and calculate the effective plugging length.

[0110] In this embodiment, a nonlinear sealing strength model is constructed: This invention references shear hysteresis theory and introduces a stress transmission attenuation coefficient. A nonlinear plugging strength model based on the exponential decay law was constructed.

[0111] Referring to the load transfer mechanism of the anchor bolt anchorage section, stress concentration and shear hysteresis effects exist during high-pressure water impact. That is, under the thrust of high-pressure water, the interfacial shear stress between the grout and the pipe wall is not equal everywhere, but decreases exponentially from the stressed end (high-pressure water end) to the distal end. Based on the shear hysteresis theory, and considering interfacial damage under high pressure, we assume the interfacial shear stress... It exhibits a nonlinear exponential distribution along the axial direction:

[0112]

[0113] Establish the equilibrium equation: the total thrust F must be equal to the total resistance along the length L.

[0114]

[0115] Right now

[0116]

[0117] Perform integration:

[0118]

[0119]

[0120] The final formula is obtained by simplification.

[0121]

[0122] Transpose

[0123]

[0124] Based on the principle of force balance (total thrust = total frictional resistance), the constitutive equations for the critical failure pressure P and the sealing length L are derived by integral derivation:

[0125]

[0126] Critical failure pressure (measured value, MPa);

[0127] : Blocking length (independent variable, precisely controlled by the device, in meters);

[0128] Pipe inner diameter (constant, m);

[0129] Peak bond strength: Characterizes the chemical bonding and mechanical interlocking ability of a material, and determines whether initial loosening occurs;

[0130] (Residual bond strength): Characterizes the sliding friction resistance after interface failure and determines the anti-slip ability after failure;

[0131] (Stress transfer attenuation coefficient): Characterizes the rate attenuation of hydrodynamic thrust along the interface. , is the core indicator for calculating the effective blocking length;

[0132] In this embodiment, the specific steps for testing and calculation using the device from Embodiment 1 are as follows:

[0133] Parameter settings: Select the grouting material to be tested and the test pipe with a specific roughness on the inner wall and an inner diameter of D.

[0134] Multi-point data acquisition (variable L measurement P): Adjust the piston position to prepare a length of... After the sealing body is grouted and cured, the piston is removed, and high-pressure water is applied until it is destroyed. The critical pressure is recorded. Clean the pipes (or replace the liner), then adjust the piston position to prepare the length. For the sealing bodies (at least 3 sets are recommended), repeat the experiment to obtain multiple sets. Data points.

[0135] Model fitting and parameter inversion: using measured data Substituting into the aforementioned nonlinear constitutive equation, and using the least squares method for nonlinear regression analysis, three key constitutive parameters of the grouting material under specific geological conditions were calculated through inversion: .

[0136] In this embodiment, the detailed operation steps for grouting sample preparation and pressure testing after piston adjustment are as follows:

[0137] In this design, the water inlet of the pipeline, i.e., connection interface 1, is simplified to end B; the grouting port 2 is simplified to end A.

[0138] Step 1: Device Assembly and Roughness Environment Construction

[0139] Pipeline pretreatment: High-pressure metal pipes with a specific JRC roughness structure prefabricated on the inner wall are selected as the test subject to simulate the mechanical interlocking characteristics of the borehole wall in real rock mass.

[0140] Piston Lubrication and Installation: Apply a uniform layer of release agent (such as petroleum jelly) to the sealing ring surface and push-pull rod surface of the removable piston head to enhance sealing and reduce frictional resistance when removing the piston later. Install the piston assembly into the pipe, install the B-end positioning cap, and allow the push-pull rod to extend out of the pipe through the positioning cap.

[0141] Step 2: Variable-length in-situ sample preparation

[0142] Precise length positioning: Based on the experimental design, the occlusion length for the current group is set as follows: Move the piston axially using the push-pull lever handle, observe the scale markings on the push-pull lever, and align them with the baseline of the positioning cover.

[0143] Boundary locking: Tighten the lateral locking screws on the positioning cover to rigidly fix the push-pull rod, making the piston a temporary rigid bottom mold during grouting.

[0144] Pressure grouting: Connect a grouting pump to end A of the pipe and inject expanding polymer grout. Maintain the grouting pressure (e.g., 0.5 MPa) for a certain period of time to allow the grout to fully penetrate into the rough texture of the pipe wall.

[0145] Step 3: Curing and In-situ Cavity Formation

[0146] Static curing: Keep the device static and wait for the slurry to react and cure to reach the predetermined strength.

[0147] In-situ cavity formation (key step): Loosen the locking screws and remove the B-end positioning cap. Use the push-pull rod to smoothly pull the piston out of the pipe axially. After the piston is removed, the space originally occupied by the piston inside the pipe is transformed into a smooth, regular high-pressure water loading cavity, and the stress-bearing end face of the grouting body remains flat and undamaged.

[0148] Step 4: Dynamic water impact test and critical pressure recording

[0149] Apply dynamic water load: Install a high-pressure water injection device at end B of the pipeline, and connect a servo high-pressure water pump and a precision pressure sensor.

[0150] Destructive test: Start the water pump to apply dynamic water pressure to the stressed end face of the grouting body. The pressure is increased step by step or linearly until the sealing body is detected to have overall slippage or structural damage.

[0151] Data recording: Record the critical failure pressure value at the moment of closure failure. .

[0152] Step 5: Iteration of multiple sets of variables and data acquisition

[0153] Iterative testing: changing the piston's positioning length (e.g.) Repeat steps S2 to S4 to obtain at least three sets of "plugging length-critical pressure" data pairs. .

[0154] Step 6: Nonlinear Model Construction and Parameter Inversion

[0155] Constitutive equations are constructed: Based on shear hysteresis theory, and considering the exponential decay of interfacial shear stress under high-pressure water thrust, a constitutive equation including peak bond strength is established. Residual bond strength and stress transmission attenuation coefficient Nonlinear constitutive equations:

[0156]

[0157] Where D is the inner diameter of the pipe and L is the sealing length.

[0158] Parameter inversion: This involves converting the multiple sets of measured data obtained in step 5 into... Substituting the above equations, and using the nonlinear curve fitting function in data analysis software such as Origin, the Levenberg-Marquardt iterative algorithm is employed with the minimization of the sum of squared residuals as the convergence objective to perform regression analysis on the formula. The parameter values ​​output by the algorithm after convergence are the three key mechanical parameters of the grouting material under the current geological model: .

[0159] This invention utilizes an internal positioning technology based on external scales (visual control), overcoming the limitation of existing pipeline grouting methods that lack visualization. By mapping the internally invisible piston position to an externally visible reading using the scale on the push-pull rod, the sealing length of the expanding polymer can be precisely set, solving the problem of quantitatively controlling the sealing body length in existing technologies. It also facilitates the replication of sealing conditions under identical circumstances.

[0160] The device design of this invention encompasses two stages: grouting and curing, and water flow impact. By adjusting the position of the piston, the entire process from specimen preparation to hydrostatic testing can be completed within the same pipe without the need to transfer the specimen, thus ensuring a consistent experimental environment.

[0161] This invention introduces a stress transfer attenuation coefficient to decouple parameters and establishes a nonlinear constitutive model that includes peak strength and residual strength.

[0162] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An experimental apparatus for testing the sealing and impact resistance properties of grouting materials, characterized in that: The experimental apparatus includes, The pressure test pipe (3) is open at both ends to accommodate grouting material and withstand fluid pressure; the inner wall of the pipe (3) has a roughened structure to simulate the real soil and rock pore wall; The piston structure includes a piston head (6) and a push-pull rod (5). The piston head (6) is located inside the pressure test pipe (3) and its outer diameter is adapted to the inner diameter of the pressure test pipe (3). One end of the push-pull rod (5) is connected to the piston head (6), and the other end extends to the outside of the pressure test pipe (3). The push-pull rod (5) is provided with scale markings. A locking mechanism is provided to lock the push-pull rod (5) relative to the pressure test pipe (3) to fix the axial position of the piston head (6) within the pressure test pipe (3).

2. The experimental apparatus for testing the sealing and impact resistance properties of grouting materials according to claim 1, characterized in that: The roughened structure is at least one of the following: grooves, knurling, sandblasting roughness, or chemical etching surface processed on the inner wall of the pressure test pipe (3).

3. The experimental apparatus for testing the sealing and impact resistance properties of grouting materials according to claim 1, characterized in that: The roughened structure is a replaceable inner liner installed inside the pressure test pipe (3), and the inner surface of the inner liner is pre-formed with a rough texture.

4. The experimental apparatus for testing the sealing and impact resistance properties of grouting materials according to claim 1, characterized in that: The locking mechanism includes a positioning cover (8) and a locking member (10). The positioning cover (8) is detachably installed at one end of the pressure test pipe (3). The positioning cover (8) has a central through hole (9) through which the push-pull rod (5) passes. The locking member (10) is provided on the positioning cover (8) for tightening and fixing the push-pull rod (5) after it passes through the central through hole (9).

5. The experimental apparatus for testing the sealing and impact resistance properties of grouting materials according to claim 4, characterized in that: The positioning cover (8) is installed on the pressure test pipe (3) by means of thread or flange connection.

6. The experimental apparatus for testing the sealing and impact resistance properties of grouting materials according to claim 1, characterized in that: The piston head (6) is provided with at least one sealing ring (7) on its outer periphery.

7. The experimental apparatus for testing the sealing and impact resistance properties of grouting materials according to claim 1, characterized in that: One end of the pressure test pipe (3) is provided with a grouting port (2), and the other end is provided with a connection interface (1) for connecting a high-pressure fluid source. The connection interface (1) is provided with threads on its outer periphery.

8. A method for testing the sealing and impact resistance properties of grouting materials, characterized in that: Using the experimental apparatus according to any one of claims 1-7, the method includes the following steps: S1: In the pressure test pipe (3), by adjusting and locking the position of the piston head (6), a grouting material plug with a specific length L is prepared; S2: After removing the piston structure, apply fluid pressure to the plug until it is destroyed, and record the critical destruction pressure P; S3: Change the position of the piston head (6), repeat steps S1 and S2 at least three times, and obtain multiple sets of measured data pairs of different sealing lengths L and their corresponding critical failure pressures P; S4: Based on the shear hysteresis theory, a nonlinear constitutive equation is established between the critical failure pressure P and the sealing length L. The nonlinear constitutive equation is as follows: Critical failure pressure (measured value, MPa); : Blocking length (independent variable, precisely controlled by the device, in meters); Pipe inner diameter (constant, m); Peak bond strength; characterizes the chemical bonding and mechanical interlocking ability of a material, and determines whether initial loosening occurs; Residual bond strength; characterizes the sliding friction resistance after interface failure and determines the anti-slip capability after failure; Stress transmission attenuation coefficient; characterizing the rate of attenuation of hydrodynamic thrust along the interface. It is the core indicator for calculating the effective blocking length. S5: Substitute the multiple sets of measured data obtained in step S3 into the nonlinear constitutive equation, perform fitting analysis, and invert to obtain... .

9. A method for testing the sealing and impact resistance properties of grouting materials according to claim 8, characterized in that: Substituting the multiple sets of measured data obtained in step S3 into the nonlinear constitutive equation, and using the least squares method for nonlinear regression analysis, the three key mechanical parameters of the grouting material under the current geological model are calculated: .

10. A method for testing the sealing and impact resistance properties of grouting materials according to claim 8, characterized in that: In step S1, by observing the scale markings on the push-pull rod (5) which is fixedly connected to the piston structure, the axial position of the piston structure within the pressure test pipe (3) is visually adjusted and determined from the outside of the pressure test pipe (3).

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