Waterproof and impermeable experimental method based on composite structure of tunnel lining and ductile membrane

Abstract

The present application relates to the technical field of waterproof impermeability experiment, in particular to a waterproof impermeability experiment method based on a tunnel lining and a flexible membrane composite structure, the present application aims at the fact that existing researches mainly focus on the properties of materials, and the research on the systematic waterproof efficiency of the membrane waterproof system under different stress states in the construction stage and the operation stage is still relatively insufficient, the present application prepares a primary support membrane structure sample and a secondary lining membrane structure sample, which respectively correspond to the tunnel construction stage and the operation stage, realizes comprehensive simulation of the different stress environments of the membrane layer, and solves the problem that the traditional experiment conditions are single and disconnected with the actual situation, the present application realizes real-time monitoring of the water seepage diffusion path, order and rate through uniformly arranged observation tubes and pressure gauges, establishes correlation analysis of the peeling pressure and the diffusion rate in combination with relevant analysis, when the correlation is strong, the diffusion rate is faster and the peeling pressure is lower, and then the evaluation of the influence of the membrane uniformity on the waterproof efficiency is realized, which provides a directional basis for the optimization of the construction process.

Description

Technical Field

[0001] This invention relates to the field of waterproof and seepage-resistant testing technology, and in particular to a waterproof and seepage-resistant testing method based on a composite structure of tunnel lining and tough spray film. Background Technology

[0002] As a crucial component of modern transportation infrastructure and underground space development, tunnel engineering's structural waterproofing performance directly impacts the project's long-term safety, durability, and operation and maintenance costs. Groundwater leakage not only erodes concrete lining structures, reducing their load-bearing capacity and service life, but can also trigger a series of chain reactions, such as internal equipment corrosion, electrical short circuits, and environmental degradation, even threatening operational safety. Traditional waterproofing technologies (such as waterproof membranes and grouting) often face challenges in practical applications, including difficulties in joint treatment, poor substrate adaptability, and low construction efficiency. Their reliability is severely tested, especially in situations requiring complex cross-sectional shapes and rapid construction.

[0003] In recent years, spray-coated waterproofing technology, as an emerging flexible waterproofing method, has shown broad application prospects in tunnels and underground engineering due to its advantages such as seamless film formation, strong adaptability, and convenient construction. This technology forms a continuous and dense spray film layer on the surface of the initial support concrete through a spraying process, effectively sealing micro-cracks and pores and preventing moisture migration. Domestic and international scholars have conducted preliminary research from multiple perspectives, including material properties, interfacial bonding, and structural impermeability. Regarding material properties, for example, existing literature discloses the influence of metakaolin on the mechanical properties of spray-coated waterproofing materials based on an integrated "initial support-waterproofing layer-secondary lining" structure; another example is the existing literature that discloses a simulated test study on the damage to the performance of spray-coated waterproofing under tunnel stress conditions using a self-designed and developed experimental device; the film-forming mechanisms of different spray-coated waterproofing materials have been summarized, highlighting their performance advantages compared to traditional methods.

[0004] However, existing research focuses on the properties of the materials themselves or the behavior of a single interface. There is a lack of research on the systematic waterproofing performance of spray membrane waterproofing systems under different stress states during the construction and operation stages, and the experimental scenarios are out of touch with real working conditions.

[0005] Especially in practical engineering, the sprayed membrane layer is often under pressure between the primary support and the secondary lining, and its resistance to water pressure stripping, water seepage behavior, and synergistic effect with the structural system are still unclear. Existing experiments only focus on whether the sprayed membrane layer fails, without monitoring the water seepage path and diffusion rate between the sprayed membrane layer and the primary support interface, nor establishing the correlation between diffusion rate and stripping pressure, thus failing to reveal the influence of key factors such as the uniformity of the sprayed membrane layer on waterproofing performance.

[0006] Therefore, it is necessary to reveal the failure mechanism and waterproofing performance of the sprayed waterproofing layer under complex stress-water pressure coupling through indoor experiments and mechanical analysis. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a waterproof and seepage-resistant experimental method based on a composite structure of tunnel lining and tough sprayed film, comprising: preparing a primary support sprayed film structure sample simulating the tunnel construction stage and a secondary lining sprayed film structure sample simulating the tunnel operation stage; the primary support sprayed film structure sample consists of a cast primary support layer and a sprayed film layer sprayed onto the bottom of the primary support layer, and the secondary lining sprayed film structure sample consists of a cast primary support layer and a secondary lining layer, with a sprayed film layer sprayed between the primary support layer and the secondary lining layer.

[0008] The test pump was connected to the water inlet pipe installed in the initial support layer. The water inlet pipe was pressurized by increasing the pressure in stages with equal amount, and pressure stabilization intervals were set for each stage of pressurization.

[0009] During the pressure stabilization process, the pressure values ​​corresponding to the peeling and puncture phenomena of the spray film layer of the primary support spray film structure sample and the pressure values ​​corresponding to the water diffusion and peeling phenomena of the secondary lining spray film structure sample are obtained, and the waterproof performance of the primary support spray film structure sample and the secondary lining spray film structure sample are determined respectively.

[0010] Furthermore, the initial support layer of the initial support spray film structure sample is pre-fabricated with fissures to simulate water seepage in the surrounding rock.

[0011] In the secondary lining sprayed film structure specimen, the primary support layer and the secondary lining layer are connected by fasteners and a pre-tightening force is provided to simulate the squeezing effect between the linings. The primary support layer of the secondary lining sprayed film structure specimen is pre-fabricated with cracks and multiple observation tubes for monitoring water leakage.

[0012] Furthermore, the water inlet pipe of the initial support layer is reserved in its middle position, and the water inlet pipe penetrates the initial support layer and communicates with the spray film layer.

[0013] The observation tubes on the secondary lining spray film structure are evenly distributed outward from the water inlet pipe as the center, and the observation tubes penetrate the initial support layer and are connected to the spray film layer.

[0014] Furthermore, the precast cracks are formed as follows: when the concrete is poured in the initial support layer, a partition coated with a release agent is inserted at a preset position. After the concrete reaches the predetermined curing state, the partition is removed to form cracks in the initial support layer.

[0015] Furthermore, the experimental steps for the initial support spray film structure sample are as follows: pressurize the water inlet pipe with an initial pressure value and maintain the initial pressure value with a first pressure stabilization interval, and then gradually increase the pressure of the water inlet pipe with a set pressure value.

[0016] During the pressure stabilization process, observe the state of the sprayed film. When the sprayed film layer of the initial support sprayed film structure sample shows bulging, record this state as the peeling state and record the corresponding pressure value as the first peeling pressure value.

[0017] Continue to pressurize the inlet pipe step by step. When the spray film layer of the initial support spray film structure sample bulges and is punctured, record this state as the puncture phenomenon and the corresponding pressure value as the puncture pressure value.

[0018] Furthermore, the first peel pressure values ​​of each initial spray film structure sample are summarized, and the smallest first peel pressure value is selected as the peel pressure value of the initial spray film structure sample.

[0019] Furthermore, the experimental steps for the double-lining spray film structure specimen are as follows: fill each observation tube with water to remove air, and install a pressure gauge on each observation tube.

[0020] The inlet pipe is pressurized with an initial pressure value and maintained at the initial pressure value with a second pressure stabilization interval. Then, the inlet pipe is pressurized step by step with a set pressure value.

[0021] During the pressure stabilization process, observe the readings of the pressure gauges at each position. When a pressure gauge registers a reading, it indicates that the spray film layer at that position has peeled off. When all pressure gauges register a reading, record the corresponding pressure value as the second peeling pressure value. At this point, the spray film layer is completely peeled off.

[0022] The minimum second peel pressure value was selected as the peel pressure value of the double-lining spray film structure sample.

[0023] Furthermore, during the pressure stabilization process, the diffusion of water in the spray film is simulated according to the order in which each observation tube appears and the order in which water seeps into each direction of the secondary lining spray film structure sample. The water diffusion area when the spray film layer is completely peeled off is determined according to the size of the sample and the distance between each observation tube and the water inlet pipe.

[0024] The time taken for the sprayed film layer to be completely peeled off was statistically analyzed, and the diffusion rate was calculated by the ratio of the water diffusion area to the time taken for the sprayed film layer to be completely peeled off. Correlation analysis was then performed based on the second peeling pressure value and the diffusion rate of each sample.

[0025] Furthermore, the correlation analysis steps are as follows: statistically analyze the second peeling pressure value and the corresponding diffusion rate of each secondary lining spray film structure sample to establish a data sample set.

[0026] The correlation coefficient between the second stripping pressure value and the diffusion rate is calculated to quantify the degree of correlation between the second stripping pressure value and the diffusion rate.

[0027] A scatter plot was drawn with diffusion rate on the horizontal axis and second peeling pressure on the vertical axis, and the trend was fitted to obtain the regression equation and coefficient of determination.

[0028] By combining the correlation coefficient and the coefficient of determination, the direction and strength of the correlation between the second stripping pressure value and the diffusion rate are evaluated.

[0029] Furthermore, the method for evaluating the correlation direction and strength between the second peeling pressure value and the diffusion rate is as follows: set upper and lower thresholds for the correlation coefficient and the determination coefficient, respectively. If the absolute value of the correlation coefficient is greater than its upper threshold and the determination coefficient is greater than its upper threshold, then the second peeling pressure value and the diffusion rate are determined to be strongly correlated.

[0030] If the absolute value of the correlation coefficient is less than its lower threshold and the coefficient of determination is less than its lower threshold, then the second stripping pressure value and the diffusion rate are determined to be weakly correlated.

[0031] If the second stripping pressure value and the diffusion rate are not among the strongly or weakly correlated cases, then the second stripping pressure value and the diffusion rate are determined to be moderately correlated.

[0032] By combining the positive and negative signs of the correlation coefficient, the direction of the correlation between the second stripping pressure value and the diffusion rate is determined simultaneously.

[0033] The beneficial effects of this system are as follows: First, by preparing primary support sprayed film structure specimens and secondary lining sprayed film structure specimens, corresponding to the tunnel construction stage and operation stage respectively, this invention achieves comprehensive simulation of different stress environments of the sprayed film layer, solving the problem of single experimental conditions and disconnection from reality in traditional experiments; among them, the secondary lining sprayed film structure specimen simulates the squeezing effect of the primary support and secondary lining on the sprayed film layer through bolt pre-tightening force, accurately simulating the stress state of the sprayed film layer under complex stress and water pressure environment, solving the limitation of traditional experiments that only consider the single water pressure effect.

[0034] Second, the present invention adopts an experimental mode of equal-volume stepwise pressurization and graded pressure stabilization intervals to ensure that the adhesion force between the sprayed film layer and the interface is fully responsive and to accurately capture critical parameter values ​​such as peel pressure and puncture pressure, thus avoiding the problem of low test accuracy caused by traditional continuous pressurization.

[0035] Third, this invention uses uniformly distributed observation tubes and pressure gauges to monitor the seepage diffusion path, sequence, and rate in real time. Combined with correlation analysis, it establishes a correlation analysis between peeling pressure and diffusion rate. When the correlation is strong, the faster the diffusion rate, the lower the peeling pressure. This allows for the evaluation of the impact of spray film uniformity on waterproofing performance and provides a directional basis for optimizing construction technology. Attached Figure Description

[0036] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the initial support spray film structure sample of the present invention.

[0038] Figure 2 This is a flowchart of the fabrication process of the initial spray film structure sample of the present invention.

[0039] Figure 3 This is a frontal schematic diagram of the model of the two-layer sprayed film structure sample of the present invention.

[0040] Figure 4 This is a top view schematic diagram of the sample of the double-lining spray film structure of the present invention.

[0041] Figure 5 This is a flowchart illustrating the fabrication process of the secondary lining spray film structure sample of the present invention.

[0042] Figure 6 This is a diagram showing the state of the initial spray film structure of the present invention from bulging to puncture.

[0043] Figure 7 This is an experimental state diagram of the sample of the double-lining sprayed film structure of the present invention.

[0044] Figure 8 This is a schematic diagram of the water seepage in the sample of the double-lining spray film structure of the present invention.

[0045] Figure 9 This is a flowchart of the waterproof and seepage-resistant experimental method of the present invention. Detailed Implementation

[0046] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0047] See Figure 9 An experimental method for waterproofing and seepage prevention based on a composite structure of tunnel lining and tough sprayed membrane includes: S100, preparing a primary support sprayed membrane structure sample simulating the tunnel construction stage and a secondary lining sprayed membrane structure sample simulating the tunnel operation stage.

[0048] Considering that after tunnel excavation, shotcrete is generally used for initial support to prevent loosening of the surrounding rock, and a waterproof layer is constructed by spraying a membrane. After the membrane hardens, it bonds tightly to the surface of the initial support to achieve a water-stopping effect. However, due to the low density of the shotcrete initial support structure itself, cracks and pores make it easy for water seepage from the surrounding rock to penetrate the initial support structure and act on the initial support-shotcrete interface, forming a water pocket. When the water pressure from the surrounding rock seepage exceeds the bonding strength of the membrane, the membrane gradually peels off the initial support interface, the water pocket gradually increases, and eventually punctures and fails. Therefore, an initial support-shotcrete structure sample is used to simulate the waterproofing and failure of the tunnel initial support-shotcrete interface.

[0049] In embodiments of the present invention, such as Figure 1 As shown, the S110 initial support sprayed film structure specimen consists of an initial support layer formed by concrete pouring and a sprayed film layer sprayed onto the bottom of the initial support layer. The initial support layer of the initial support sprayed film structure specimen has pre-fabricated cracks simulating water seepage in the surrounding rock. The water inlet pipe of the initial support layer is reserved in its middle position, and the water inlet pipe penetrates the initial support layer and communicates with the sprayed film layer. It should be noted that... Figure 1 The rectangular section in the upper middle part is the initial support layer. A water inlet pipe is installed in the middle of the initial support layer. The lower part of the water inlet pipe is a prefabricated crack. A spray film layer is sprayed onto the bottom of the initial support layer.

[0050] For example, see Figure 2 The specific steps for fabricating the initial support sprayed film structure sample are as follows: S111. Fabricate a 60cm×60cm×10cm concrete template. Drill a hole in the center of the base plate and pre-install a 1 / 4-inch pipe as a water inlet pipe. Place the outlet end of the 1 / 4-inch pipe 2cm away from the top surface of the template (for prefabricating cracks), and tie the top of the water pipe with geotextile to prevent the pipe from being blocked when pouring concrete.

[0051] S112. Pour C25 concrete slabs to simulate initial support shotcrete. During pouring, use a vibrator to fully compact the concrete. After pouring, brush release agent on both sides of a 1mm thick aluminum sheet and insert it into the center of the concrete slab to leave a crack. The bottom of the aluminum sheet is attached to the outlet end of the 1 / 4-inch pipe.

[0052] S113. Concrete curing: After the initial setting of the concrete, the aluminum sheet is moved up and down to prevent it from becoming stuck after the concrete hardens. The aluminum sheet is removed after 3-5 days of curing, creating cracks in the initial support structure. These cracks simulate natural cracks or pores in the tunnel's initial support structure caused by insufficient concrete density in actual engineering, providing realistic simulation conditions for subsequent simulations of water seepage through the cracks acting on the initial support-sprayed membrane interface.

[0053] Furthermore, by pre-setting pre-fabricated cracks with specific sizes and locations, the shape and distribution of seepage channels can be controlled, making the action mode and stress state of seepage water on the sprayed film layer during the experiment closer to the phenomenon of interface water pressure concentration caused by defects in the initial support structure itself in reality. This allows for a more accurate assessment of the adhesion performance, peel resistance, and ultimate bearing capacity against water pocket formation and puncture damage of the sprayed film layer on the interface of the initial support where cracks exist.

[0054] S114. After the concrete has been cured for 28 days, a toughness spray film is sprayed onto the concrete surface in two stages. After the first layer of film is dry, the second layer of film is sprayed to the designed thickness. The concrete is then cured at room temperature for 7 days to form a sample of the initial support spray film structure. Figure 2 The last three state diagrams are respectively: the first layer of film has been sprayed, the second layer of film has been sprayed, and the initial support sprayed film structure sample has been formed after curing.

[0055] Considering that secondary lining pouring is required during the tunnel operation phase, the poured secondary lining structure of the tunnel exerts a squeezing effect on the sprayed membrane. Due to the high roughness of the initial support interface itself, the load environment borne by the waterproof sprayed membrane under the squeezing action of the initial support layer and the secondary lining layer is often complex and variable. Therefore, a secondary lining sprayed membrane structure sample was used to simulate the tunnel initial support-sprayed membrane-secondary lining interface model experiment.

[0056] To further simulate the compressive stress environment of the primary support-sprayed film-secondary lining during tunnel operation, this invention designs a secondary lining sprayed film structure specimen.

[0057] The S120 secondary lining sprayed film structure sample consists of an upper and lower cast-in-place primary support layer and a secondary lining layer, with a sprayed film layer applied between the primary support layer and the secondary lining layer. Please refer to [link / reference]. Figure 3 In the secondary lining spray film structure specimen, the primary support layer and the secondary lining layer are connected by fasteners and provided with pre-tightening force to simulate the squeezing effect between the linings. The primary support layer of the secondary lining spray film structure specimen has pre-fabricated cracks and multiple observation tubes for monitoring water leakage. The observation tubes on the secondary lining spray film structure are evenly extended outward from the water inlet pipe as the center. The observation tubes penetrate the primary support layer and are connected to the spray film layer.

[0058] For example, see Figure 5 The specific steps for fabricating the secondary lining sprayed film structure sample are as follows: S121, Fabricate an 80cm×80cm×20cm concrete formwork, drill a pre-drilled water inlet pipe in the center of the bottom of the formwork, and proceed according to... Figure 4 The arrangement includes reserving 8 observation tubes around the perimeter and 4 bolt holes at the corners. Figure 4 The number in the text is the observation tube number.

[0059] S122. Both the inlet pipe and the observation pipe are 1 / 4-inch pipes. During installation, the outlet end of the inlet pipe is 2cm away from the top surface of the formwork (for prefabricating cracks). One end of the observation pipe is connected to a pressure gauge, and the other end is flush with the top surface of the formwork. All pipe ends are bound with geotextile to prevent blockage during concrete pouring. PVC water pipes are inserted at the bolt hole locations to pre-drill bolt holes.

[0060] S123. Pour C25 concrete slabs to simulate the initial support shotcrete. After pouring, use a vibrator to fully compact the concrete. The initial support concrete pouring height is set to 10cm, which is flush with the height of the water pipe in the observation hole. After pouring, brush release agent on both sides of a 1mm thick aluminum sheet and insert it into the center of the concrete slab to leave a crack. The bottom of the aluminum sheet is attached to the water outlet of the inlet pipe.

[0061] S124. Concrete curing: After the concrete has initially set, gently pull the aluminum sheet up and down to prevent it from becoming impossible to remove once the concrete has solidified. Remove the aluminum sheet after 3-5 days of curing, which will create cracks in the initial support structure.

[0062] S125. After the concrete has been cured for 28 days, apply a toughness coating to the concrete surface in two coats. After the first coat is dry to the touch, apply the second coat to the designed thickness and cure at room temperature for 7 days.

[0063] S126. After the spray film curing is completed, C35 concrete is poured to simulate the secondary lining structure of the tunnel. During pouring, the concrete is fully vibrated and compacted with a vibrator. After pouring, it is cured for 28 days.

[0064] S127. After the secondary lining concrete has been cured, remove the external formwork, take out the PVC water pipe, insert a 24mm diameter bolt and tighten the nut to apply pressure and preload, forming a secondary lining spray film structure sample.

[0065] By preparing primary support sprayed membrane structure specimens and secondary lining sprayed membrane structure specimens, we can understand the environment and seepage conditions at the primary support-sprayed membrane interface during tunnel construction, as well as the complex stress state under compressive loads during operation. This provides a basis for subsequent waterproof and seepage-resistant performance testing and failure judgment, ensuring that the experimental results can truly reflect the actual working conditions of the composite waterproof structure.

[0066] S200. Connect the test pump to the inlet pipe and pressurize the inlet pipe by increasing the pressure in stages in equal amounts, with each stage of pressurization having a pressure stabilization interval.

[0067] Considering that the waterproof and seepage-resistant test is a test process with progressive pressure, the method of applying equal pressure at each stage can more accurately obtain the change characteristics of the sprayed film structure under different water pressures. In addition, the set pressure stabilization interval can provide sufficient pressure time for the sprayed film structure and avoid inaccurate experimental data due to sudden pressure increases.

[0068] In some embodiments, a 3DSY-60 electric pressure testing pump is connected to the inlet pipe, and the water pressure loading range of the pressure testing pump is set to 0-6.0 MPa.

[0069] S300, The experimental steps for the initial support spray film structure sample are as follows: S310, pressurize the water inlet pipe with an initial pressure value and maintain the initial pressure value with a first pressure stabilization interval, and then gradually increase the pressure of the water inlet pipe with a set pressure value. For example, the initial pressure value is set to 0.25 MPa, the first pressure stabilization interval is 3 minutes, and the pressure value set for each stage is 0.25 MPa.

[0070] In an embodiment of the present invention, the tunnel will have water drainage measures during the excavation process, and the groundwater level will be lowered to a lower level. The loading will start from a lower pressure, which can more realistically simulate the initial stage of the waterproof layer gradually bearing the seepage pressure after the initial support is completed. Therefore, the initial pressure value is set to 0.25MPa.

[0071] To ensure that the sprayed film structure has sufficient time to adapt to pressure and deformation after each pressure level is applied, and that the adhesion between the sprayed film layer and the initial support layer fully responds to the current water pressure, the first pressure stabilization interval is set to 3 minutes.

[0072] Each pressure gradient is set at 0.25 MPa. This pressure gradient setting ensures the accuracy of experimental data, facilitates the capture of minute changes and critical failure points of the sprayed membrane structure at different pressure stages, and allows for a comprehensive evaluation of the waterproof performance of the sprayed membrane structure within a reasonable experimental time.

[0073] S320. Observe the state of the sprayed film during the voltage stabilization process, such as... Figure 6 As shown, when bulges appear in the sprayed film layer of the initial support sprayed film structure sample, this state is recorded as the peeling state, and the corresponding pressure value is recorded as the first peeling pressure value. It should be noted that... Figure 6 The diagram shows the process of the spray film from bulging to puncture. The numbers marked in the diagram are the numbers of the spray film bulges, and the structures inside the boxes are magnified views of the corresponding circled parts in the diagram. Figure 6 The states in the diagram are as follows: initial state of the sample → bulging of the sprayed film → new bulging of the sprayed film → numerous bulging of the sprayed film → puncture of the sprayed film → top view of the punctured sprayed film.

[0074] In actual situations at the tunnel primary support-sprayed membrane interface, when seepage water from the surrounding rock penetrates through pre-fabricated cracks or pores in the primary support layer to the surface of the sprayed membrane layer, local water pressure is generated between the sprayed membrane layer and the primary support layer. As the amount of seepage increases, the water pressure gradually accumulates. When the water pressure exceeds the bonding strength between the sprayed membrane layer and the primary support layer, the sprayed membrane layer will separate from the primary support layer, and bulges will form in the sprayed membrane layer under the action of water pressure. Therefore, the bulging of the sprayed membrane layer reflects the failure of the bonding between the sprayed membrane layer and the primary support layer, which is a characteristic of the peeling and failure of the sprayed membrane layer.

[0075] S330, such as Figure 6 As shown, the inlet pipe is pressurized step by step. When the spray film layer of the initial support spray film structure sample bulges and punctures, this state is recorded as a puncture phenomenon, and the corresponding pressure value is recorded as the puncture pressure value. It should be noted that... Figure 6 The diagram shows the state of the spray film from bulging to puncture, with numbers used to mark the bulges.

[0076] The puncture pressure value represents the ultimate bearing capacity of the sprayed membrane layer under continuous water pressure, from interface peeling to the final loss of its waterproof function. This value reflects the tensile strength, tear resistance, and ultimate force of the sprayed membrane and its bonding performance with the initial support layer. By measuring the puncture pressure value, during the tunnel construction stage, when there are defects such as cracks in the initial support structure, it can reflect the performance of the sprayed waterproof membrane layer in resisting the seepage pressure of the surrounding rock and preventing large-scale leakage, providing data basis for optimizing the construction process and waterproof performance.

[0077] S340. Summarize the first peel pressure values ​​of each initial support spray film structure sample, and select the smallest first peel pressure value as the peel pressure value of the initial support spray film structure sample. Similarly, summarize the puncture pressure values ​​of each group, and select the smallest value as the puncture pressure value of the initial support spray film structure sample.

[0078] For example, to verify the reliability of the experimental method of the present invention, three groups of samples were selected. The test process showed that when the applied water pressure was 0.5-0.75 MPa, the sprayed film bulged; when the pressure was increased to 3.25-5 MPa, the sprayed film suffered puncture damage. Based on these results, it can be concluded that the first peel pressure value of the initial support sprayed film structure sample is 0.5 MPa; and the breaking strength of the tough waterproof coating can reach 3.25 MPa.

[0079] Selecting the minimum first peel pressure value as the peel pressure value for the initial support sprayed membrane structure specimen reflects the weakest point in the waterproofing of the specimen under the most unfavorable conditions. This provides a basis for evaluating the ability of the sprayed waterproofing layer to resist seepage pressure during the construction stage and offers a reference for setting safe waterproofing parameters in tunnel waterproofing construction. Furthermore, by summarizing the pressure values ​​of multiple specimens, the interference of individual differences on the experimental results can be effectively eliminated, ensuring the reliability of the selected peel pressure value.

[0080] This invention simulates the actual stress and fracture environment at the initial support-sprayed membrane interface during tunnel construction, demonstrating the entire process of the sprayed membrane layer from initial peeling to final puncture failure. By setting initial pressure values, progressively increasing pressure values, and pressure stabilization intervals, it not only realistically simulates the gradual accumulation of seepage pressure in the surrounding rock but also captures the state changes of the sprayed membrane layer at different pressure stages, making the determination of the first peeling pressure value and the puncture pressure value more accurate.

[0081] In summary, due to the low groundwater pressure during tunnel construction, the sprayed membrane will not peel off under this pressure after application. If water seepage occurs during construction, the low water pressure will prevent peeling and water penetration, making the seepage area a weak point. In this case, re-spraying the affected area can strengthen the membrane. Therefore, this tough waterproof coating material has high waterproof performance.

[0082] S400, the experimental steps for the double-lining sprayed film structure sample are as follows: (See attached document) Figure 7 S410. Fill each observation tube with water to remove air, and install a pressure gauge on each observation tube. Initially, the pressure gauge reading is 0. When a pressure gauge starts to display a reading, the corresponding observation tube is connected to the water inlet pipe.

[0083] S420. Pressurize the inlet pipe with an initial pressure value and maintain the initial pressure value with a second pressure stabilization interval. Then, pressurize the inlet pipe step by step with a set pressure value. For example, the initial pressure value is set to 0.25MPa, the second pressure stabilization interval is 10 minutes, and the pressure value set for each stage is 0.25MPa.

[0084] Considering the continuous compression effect of the pre-tightening force on the sprayed film layer under the secondary lining sprayed film structure specimen, the mechanical response of the sprayed film layer is more complex under the combined action of bidirectional compression and water pressure. The stress transmission and deformation between the interfaces require a longer time to reach a stable state. Therefore, compared with the primary support sprayed film structure specimen, the second pressure stabilization interval of the secondary lining sprayed film structure specimen is set to be longer. This can ensure that the adhesion, friction and deformation of the sprayed film layer between the primary support and the secondary lining interface are reflected, so that the stress state of the sprayed film layer under each pressure level tends to be stable, thereby more accurately capturing the water leakage phenomenon caused by pressure transmission.

[0085] S430. During the pressure stabilization process, observe the readings of the pressure gauges at each position. When a pressure gauge produces a reading, it indicates that the spray film layer at that position has peeled off. When all pressure gauges produce a reading, record the pressure value corresponding to this time as the second peeling pressure value. At this time, the spray film layer is completely peeled off. Figure 8 The image shows the water seepage state of the double-lining sprayed film structure sample.

[0086] Under water pressure, the sprayed film layer of the primary support-sprayed film-secondary lining composite structure undergoes interfacial peeling. Seepage water will spread along the damaged channels or peeling interfaces between the primary support layer and the sprayed film layer, forming water channeling. When the pressure gauge of the observation tube generates a reading, it indicates that water has passed through the sprayed film layer to the location of the observation tube.

[0087] When all pressure gauges register a reading, it indicates that water can pass through the spray membrane structure without obstruction, marking the peeling of the spray membrane. The reason why this invention records the pressure value when all observation tubes register a reading as the second peeling pressure value is that the spray membrane is pre-tightened by bolts in the secondary lining, making it under the compression of the primary support layer and the secondary lining layer. As a result, the bond between the spray membrane and the primary support interface is tighter, and the interface stress is more complex. The appearance of a reading on a single observation tube only represents water seepage in a local weak area. However, at this time, the overall bonding surface between the spray membrane and the primary support layer has not failed, and it does not mean that the overall waterproofing of the structure has failed.

[0088] Meanwhile, the purpose of the experiment on the secondary lining spray film structure specimen is to obtain the state of overall peeling of the spray film. That is, when all observation points have readings, it means that water has spread throughout the spray film, the overall bonding surface between the spray film and the primary support layer has completely failed, and the constraint effect of the secondary lining can no longer prevent water from spreading. The peeling water pressure at this time is the true peel resistance of the specimen.

[0089] S440. The minimum second peel pressure value is selected as the peel pressure value for the double-lining sprayed film structure sample. Selecting the minimum value as the peel pressure value is also based on the most unfavorable condition for this sample.

[0090] This invention simulates the primary support-sprayed membrane-secondary lining structure of a tunnel during operation, examining the peeling of the sprayed membrane layer under the combined effects of continuous compression from bolt preload and water pressure. Multiple observation tubes and corresponding pressure gauges monitor the diffusion path and range of seepage water at the interface between the sprayed membrane layer and the primary support layer. Furthermore, by setting the second pressure stabilization interval to 10 minutes, the invention fully considers the hysteresis and complexity of the deformation of the sprayed membrane layer under bidirectional compression, ensuring that after each pressure level is applied, pressure transmission between the interfaces, deformation of the sprayed membrane layer, and seepage diffusion all reach a stable state, thereby accurately obtaining the second peeling pressure value of the sprayed membrane layer.

[0091] S500. During the pressure stabilization process, the diffusion of water in the spray film is simulated according to the order of appearance of each observation tube and the order of water seepage in each direction of the secondary lining spray film structure sample. The water diffusion area when the spray film layer is completely peeled off is determined according to the size of the sample and the distance between each observation tube and the water inlet pipe.

[0092] In an embodiment of the present invention, the specific method for determining the water diffusion area when the spray film layer is completely peeled off is as follows: S501, a two-dimensional rectangular coordinate system is established with the center of the sample plane (i.e., the position of the water inlet pipe) as the origin of the coordinate system, wherein the X-axis is along the east-west direction and the Y-axis is along the north-south direction.

[0093] S502. During the pressure stabilization process, record the time sequence of the first readings of the pressure gauges in the 8 observation tubes, as well as the time sequence of the first water seepage in the four directions of the sample (east, south, west, and north), and mark the initial position of the water seepage.

[0094] S503. Based on the above two-dimensional rectangular coordinate system, the actual positions of the 8 observation pipes and the four directional seepage points are converted into coordinate values.

[0095] S504. The observation points / seepage points that show readings at the same time are considered as the positions reached before diffusion at that time. The envelope (or fitted boundary) connecting these points is used as the diffusion profile at that time to determine the diffusion pattern. The diffusion area at complete peeling is the area enclosed by all observation points showing readings on the outermost layer and edge seepage points.

[0096] S505. Divide the sample plane into a uniform grid of 10mm × 10mm and count the number of complete grids covered by the diffusion morphology.

[0097] S506. For incomplete grids at the edges of diffusion patterns, the proportion estimation method is used. Edges that account for more than 50% of the area of ​​complete grids are counted as complete grids, and otherwise they are counted as 0.5 complete grids. The total area of ​​incomplete grids is calculated, and the sum of the area of ​​complete grids and the total area of ​​incomplete grids is taken as the total diffusion area.

[0098] The above analysis method can quantify the total diffusion area with a relatively simple calculation method, and the calculation error range is within an acceptable range and does not affect the subsequent correlation analysis.

[0099] S507. If water seepage occurs around the edges of the sample, the area of ​​the sample shall be used as the total diffusion area.

[0100] S510. Statistically calculate the time taken for the sprayed film layer to be completely peeled off, and calculate the diffusion rate by the ratio of the water diffusion area to the time taken for the sprayed film layer to be completely peeled off. Perform correlation analysis based on the second peeling pressure value and diffusion rate of each sample.

[0101] In an embodiment of the present invention, the time taken for the spray film layer to be completely peeled off is: the cumulative time from the start of pressurization in the water inlet pipe to the appearance of readings in all observation pipes, i.e., the product of the number of pressurization stages and the second pressure stabilization interval (the second pressure stabilization interval is 600s).

[0102] S520. The correlation analysis steps are as follows: S521. Statistically analyze the second peeling pressure value and the corresponding diffusion rate of each secondary lining spray film structure sample to establish a data sample set.

[0103] S522. Determine the distribution characteristics of the data sample set. If the data conforms to a normal distribution, use the Pearson correlation coefficient to calculate the correlation coefficient between the second peeling pressure value and the diffusion rate. If it is not normally distributed, use the Spearman rank correlation coefficient to calculate the correlation coefficient between the second peeling pressure value and the diffusion rate. Then quantify the degree of correlation between the second peeling pressure value and the diffusion rate. The closer the absolute value of the correlation coefficient is to 1, the stronger the correlation. A positive correlation coefficient indicates a positive correlation, and a negative correlation coefficient indicates a negative correlation.

[0104] S523. Plot a scatter plot with diffusion rate on the horizontal axis and second peeling pressure on the vertical axis, and fit the trend to obtain the regression equation and coefficient of determination.

[0105] In an embodiment of the present invention, the determination coefficient is analyzed as follows: the mean seepage diffusion rate is calculated based on the data sample set. and the average value of the second peeling pressure .

[0106] The least squares method is used to determine the linear regression equation. , Let v represent the predicted value of the second stripping pressure, v represent the seepage diffusion rate, a represent the regression slope, and b represent the regression intercept; the formula for calculating the regression slope a is: .

[0107] in Let represent the water diffusion rate of the i-th sample, where i = 1, 2, ..., n, and n represents the total number of samples. This represents the second peel pressure value of the i-th sample.

[0108] The formula for calculating the regression intercept b is: .

[0109] Calculate the total sum of squares (SST). ,in The second peel pressure value of the i-th sample is the squared deviation from the mean; the regression sum of squares (SSR) is calculated. ,in This represents the predicted second peel pressure value for the i-th sample. .

[0110] Calculate the coefficient of determination , , The closer the coefficient of determination is to 1, the better the linear regression equation fits the data, and the stronger the linear correlation between P and v.

[0111] S524. Combining the correlation coefficient and the coefficient of determination, evaluate the direction and strength of the correlation between the second stripping pressure value and the diffusion rate. In the above analysis, the correlation coefficient determines the direction and strength, while the coefficient of determination reflects the reliability of the fit. Using a combined approach to analyze the correlation can complement each other, thereby avoiding misjudgment.

[0112] In an embodiment of the present invention, the method for evaluating the correlation direction and correlation strength between the second stripping pressure value and the diffusion rate is as follows: setting upper and lower thresholds for the correlation coefficient and the coefficient of determination, respectively; for example, the upper threshold for the correlation coefficient is set to 0.7, the lower threshold for the correlation coefficient is set to 0.3, the upper threshold for the coefficient of determination is set to 0.6, and the lower threshold for the coefficient of determination is set to 0.2.

[0113] By combining the positive and negative signs of the correlation coefficient, the direction of the correlation between the second stripping pressure value and the diffusion rate is determined simultaneously; a positive correlation coefficient indicates a positive correlation, and a negative correlation coefficient indicates a negative correlation.

[0114] If the absolute value of the correlation coefficient is greater than its upper threshold and the coefficient of determination is greater than its upper threshold, then the second peel pressure value and the diffusion rate are determined to be strongly correlated. Strong correlation indicates that the uniformity of the spray film application is the main factor affecting the waterproof performance, while the diffusion rate directly reflects the adhesion between the spray film and the initial support interface. The faster the diffusion rate, the more local weak areas there are and the more uneven the adhesion, which leads to a significant reduction in peel pressure.

[0115] Therefore, during construction, it is necessary to prioritize increasing the coating thickness and improving the flatness of the substrate to reduce local defects. The peel resistance of the spray film can be directly improved by reducing the diffusion rate.

[0116] If the absolute value of the correlation coefficient is less than its lower threshold and the coefficient of determination is less than its lower threshold, then the second peel pressure value is determined to be weakly correlated with the diffusion rate. A weak correlation indicates that the effect of the diffusion rate on the peel pressure is negligible. The peel pressure of the sprayed film is mainly dominated by parameters such as the bonding strength and toughness of the material itself or the squeezing effect of the secondary lining structure, and has very little correlation with the diffusion process.

[0117] If the second peel pressure value and the diffusion rate are not in the strong or weak correlation category, then the second peel pressure value and the diffusion rate are determined to be moderately correlated. Moderate correlation indicates that the diffusion rate has a significant impact on the peel pressure, but it is not the only influencing factor. There are other influencing factors such as the magnitude of the secondary lining pre-tightening force, the roughness of the initial support base surface, and the curing time of the sprayed film.

[0118] For example, this invention selects three groups of double-lined spray film structure samples. The pressure gauges of the first group all showed readings at 3.25 MPa, and the diffusion area was 629552 mm². 2 The duration was 130 minutes, and the diffusion rate was 80.7 mm. 2 / s; When all the pressure gauges in the second group showed readings, the pressure was 3MPa, and the diffusion area was 623671mm². 2 The duration was 120 minutes, and the diffusion rate was 86.6 mm. 2 / s; When all the pressure gauges in the third group showed readings, the pressure was 2.25 MPa, and the diffusion area was 620499 mm². 2 The duration was 90 minutes, and the diffusion rate was 114.9 mm. 2 / s.

[0119] The second peel pressure values ​​and diffusion rates of the three sets of double-lined sprayed film structure samples above conform to a normal distribution. The Pearson correlation coefficient was used for calculation: the mean peel pressure and the mean diffusion rate were calculated separately, and the covariance was obtained; then the standard deviation of peel pressure and the standard deviation of diffusion rate were calculated separately, and the standard deviation of peel pressure and the standard deviation of diffusion rate were multiplied; then the ratio of the covariance to the product was used as the correlation coefficient, and the correlation coefficient was calculated to be approximately -0.96. The calculation of the Pearson correlation coefficient is a prior art and will not be elaborated on here.

[0120] The coefficient of determination obtained using the above-mentioned method is approximately 0.936, thus indicating a strong negative correlation. The diffusion rate is strongly negatively correlated with the second peel pressure, meaning that the faster the diffusion rate, the lower the peel pressure. Therefore, the uniformity of the spray coating is a key factor in controlling the waterproof and seepage-resistant performance. It is necessary to improve the flatness of the initial support surface and reduce the seepage diffusion rate by optimizing the spraying process, such as multiple sprayings and controlling the surface drying time, thereby increasing the peel pressure.

[0121] In summary, the peel strength of the primary support-spray film-secondary lining structure can reach between 2.25MPa and 3.25MPa. When the spray film is not applied evenly, the peel strength varies in different parts. In some areas, the peel water pressure can reach 3.25MPa, which has a good anti-water-crossing effect.

[0122] When the sprayed membrane is subjected to the extrusion pressure of the primary support and the supporting force of the secondary lining, the peel water pressure of the sprayed membrane can be increased by 1.75-2.75 MPa, significantly improving its waterproofing performance. Therefore, the secondary lining should be applied as soon as possible during construction to allow the tough waterproof coating to exert its best waterproofing performance.

[0123] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention, which are still covered within the protection scope of the present invention.

Claims

1. A waterproof and seepage-resistant experimental method based on a composite structure of tunnel lining and tough sprayed membrane, characterized in that, include: The primary support sprayed film structure specimen and the secondary lining sprayed film structure specimen of the tunnel operation stage were prepared to simulate the tunnel construction stage. The primary support sprayed film structure specimen consists of a primary support layer formed by casting and a sprayed film layer attached to the bottom of the primary support layer. The secondary lining sprayed film structure specimen consists of a primary support layer and a secondary lining layer cast at the top and bottom, with a sprayed film layer attached between the primary support layer and the secondary lining layer. The test pump was connected to the water inlet pipe installed in the initial support layer, and the water inlet pipe was pressurized by increasing the pressure in stages with equal amount, and pressure stabilization intervals were set for each stage of pressurization. During the pressure stabilization process, the pressure values ​​corresponding to the peeling and puncture phenomena of the spray film layer of the primary support spray film structure sample and the pressure values ​​corresponding to the water diffusion and peeling phenomena of the secondary lining spray film structure sample are obtained to determine the waterproof performance of the primary support spray film structure sample and the secondary lining spray film structure sample respectively. The primary support layer of the secondary lining spray film structure sample is pre-fabricated with cracks and multiple observation tubes for monitoring water leakage, and each observation tube is equipped with a pressure gauge. During the pressure stabilization process of the test sample of the double-lined spray film structure, observe the readings of the pressure gauges at each position. When the pressure gauges produce a reading, it indicates that the spray film layer at that position has peeled off. When all pressure gauges produce a reading, record the pressure value corresponding to this time as the second peeling pressure value. At this time, the spray film layer is completely peeled off. During the pressure stabilization process, the diffusion of water in the spray film is simulated according to the order of appearance of each observation tube and the order of water seepage in each direction of the secondary lining spray film structure sample. The water diffusion area when the spray film layer is completely peeled off is determined according to the size of the sample and the distance between each observation tube and the water inlet pipe. The time taken for the sprayed film layer to be completely peeled off was statistically analyzed, and the diffusion rate was calculated by the ratio of the water diffusion area to the time taken for the sprayed film layer to be completely peeled off. Correlation analysis was performed based on the second peeling pressure value and the diffusion rate of each sample. The correlation analysis steps are as follows: The second peeling pressure value and the corresponding diffusion rate of each secondary lining spray film structure sample were statistically analyzed to establish a data sample set; Calculate the correlation coefficient between the second stripping pressure value and the diffusion rate to quantify the degree of correlation between the second stripping pressure value and the diffusion rate; A scatter plot was drawn with diffusion rate on the horizontal axis and second peeling pressure on the vertical axis, and the trend was fitted to obtain the regression equation and the coefficient of determination. By combining the correlation coefficient and the coefficient of determination, the direction and strength of the correlation between the second stripping pressure value and the diffusion rate are evaluated.

2. The waterproofing and seepage-resistant experimental method based on the composite structure of tunnel lining and tough sprayed membrane according to claim 1, characterized in that, The initial support layer of the initial support spray film structure sample is pre-fabricated with fissures to simulate water seepage in the surrounding rock. In the secondary lining spray film structure specimen, the primary support layer and the secondary lining layer are connected by fasteners and a pre-tightening force is provided to simulate the compression effect between the linings.

3. The waterproofing and seepage-resistant experimental method based on the composite structure of tunnel lining and tough sprayed membrane according to claim 2, characterized in that, The water inlet pipe of the initial support layer is reserved in the middle position, and the water inlet pipe passes through the initial support layer and is connected to the spray film layer. The observation tubes on the secondary lining spray film structure are evenly distributed outward from the water inlet pipe as the center, and the observation tubes penetrate the initial support layer and are connected to the spray film layer.

4. The waterproofing and seepage-resistant experimental method based on the composite structure of tunnel lining and tough sprayed film according to claim 2, characterized in that, The precast cracks are formed as follows: when the concrete is poured in the initial support layer, a partition coated with a release agent is inserted at a preset position. After the concrete reaches the predetermined curing state, the partition is removed to form cracks in the initial support layer.

5. The waterproofing and seepage-resistant experimental method based on the composite structure of tunnel lining and tough sprayed membrane according to claim 1, characterized in that, The experimental steps for the initial support spray film structure specimen are as follows: The inlet pipe is pressurized using an initial pressure value, and the initial pressure value is maintained at the first pressure stabilization interval. Then, the inlet pipe is pressurized step by step using a set pressure value. During the pressure stabilization process, observe the state of the sprayed film. When the sprayed film layer of the initial support sprayed film structure sample shows bulging, record this state as the peeling state and record the corresponding pressure value as the first peeling pressure value. Continue to pressurize the inlet pipe step by step. When the bulge of the spray film layer of the initial support spray film structure sample shows puncture damage, the state at this time is recorded as the puncture phenomenon, and the corresponding pressure value at this time is recorded as the puncture pressure value.

6. The waterproofing and seepage-resistant experimental method based on the composite structure of tunnel lining and tough sprayed membrane according to claim 5, characterized in that, The first peel pressure values ​​of each initial spray film structure sample are summarized, and the smallest first peel pressure value is selected as the peel pressure value of the initial spray film structure sample.

7. The waterproofing and seepage-resistant experimental method based on the composite structure of tunnel lining and tough sprayed membrane according to claim 2, characterized in that, The experimental steps for the double-lining sprayed film structure specimen are as follows: Fill each observation tube with water to remove air, and install a pressure gauge on each observation tube; The inlet pipe is pressurized with an initial pressure value and maintained at the initial pressure value with a second pressure stabilization interval. Then, the inlet pipe is pressurized step by step with a set pressure value. During the pressure stabilization process, observe the readings of the pressure gauges at each position. Record the pressure value corresponding to when all pressure gauges produce a reading as the second peeling pressure value. At this time, the sprayed film layer is completely peeled off. The minimum second peel pressure value was selected as the peel pressure value of the double-lining spray film structure sample.

8. The waterproofing and seepage-resistant experimental method based on the composite structure of tunnel lining and tough sprayed film according to claim 1, characterized in that, The method for evaluating the direction and strength of the correlation between the second stripping pressure value and the diffusion rate is as follows: Set upper and lower thresholds for the correlation coefficient and the coefficient of determination respectively. If the absolute value of the correlation coefficient is greater than its upper threshold and the coefficient of determination is greater than its upper threshold, then the second stripping pressure value and the diffusion rate are determined to be strongly correlated. If the absolute value of the correlation coefficient is less than its lower threshold and the coefficient of determination is less than its lower threshold, then the second stripping pressure value and the diffusion rate are determined to be weakly correlated. If the second stripping pressure value and the diffusion rate are not in any of the strongly or weakly correlated categories, then the second stripping pressure value and the diffusion rate are determined to be moderately correlated. By combining the positive and negative signs of the correlation coefficient, the direction of the correlation between the second stripping pressure value and the diffusion rate is determined simultaneously.

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