Anti-seepage construction method for diversion tunnel of high-altitude hydropower station

Abstract

The invention relates to the technical field of hydropower engineering construction, in particular to an anti-seepage construction method for a diversion tunnel of a high-altitude hydropower station. According to the method, a temperature compensation mechanism under a high-altitude environment, a material curing regulation and control technology under low air pressure and an environment parameter dynamic monitoring system are introduced, meanwhile, a multi-component composite anti-seepage material system is adopted, and technologies such as surface pretreatment, deep grouting and interface reinforcing agent coating are combined; a real-time data acquisition and intelligent construction control platform is constructed by combining various monitoring devices such as a displacement sensor, a pore water pressure gauge and an ultrasonic compactness detector, so that the seepage-proofing construction process can stably adapt to complex conditions such as high altitude, low air temperature and low air pressure, the overall construction quality and reliability are greatly improved, and the construction cost is reduced. And the long-term anti-seepage effect of high strength, high toughness, freeze thawing resistance and water pressure impact resistance is achieved.

Description

Technical Field

[0001] This invention relates to the field of hydropower engineering construction technology, and more specifically, to a method for seepage prevention construction of water diversion tunnels in high-altitude hydropower stations. Background Technology

[0002] In existing hydropower engineering construction technology, methods such as mechanical shotcreting, borehole grouting, and localized seepage treatment are commonly used for tunnel seepage prevention and reinforcement. For example, a search revealed that application number CN201711336192.3 provides a tunnel seepage prevention device and seepage treatment method. This device consists of a power drive unit, a shotcreting unit, and a portable operating gun. Through the cooperation of a dual-drive drilling machine and a shotcreting drilling machine, it achieves localized drilling, shotcreting, and grouting treatment at the seepage location in the tunnel. This method features independent structure, convenient operation, no damage to the rock mass structure, and high seepage prevention efficiency. It can quickly treat seepage points and has certain application value in general tunnel engineering.

[0003] However, the aforementioned traditional technologies are mainly designed for localized seepage control under conventional operating conditions. Their seepage prevention effect relies on localized spraying or pipe grouting, lacking adaptability to the complex environmental factors at high altitudes. They struggle to ensure grout diffusion, curing strength, and interfacial bonding performance under low temperature and low pressure conditions. Furthermore, these technologies generally lack a systematic seepage prevention design for the overall tunnel structure, failing to achieve uniform formation and long-term stable maintenance of a large-scale seepage prevention layer. This makes it difficult to meet the long-term safety requirements of high-altitude hydropower station water diversion tunnels under high water pressure and high deformation environments. Therefore, there is an urgent need for a construction method that can adapt to the characteristics of high-altitude environments, possesses dynamic control capabilities, and achieves high-density seepage prevention throughout the tunnel, overcoming the shortcomings of traditional technologies. Summary of the Invention

[0004] In view of the above-mentioned problems in the existing technology, the purpose of this invention is to provide a seepage prevention construction method for water diversion tunnels in high-altitude hydropower stations. This method can not only adapt to the characteristics of high-altitude environment, but also has dynamic control capability, and can achieve high-density seepage prevention of the entire tunnel.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows: A method for seepage prevention construction of a water diversion tunnel for a high-altitude hydropower station, the method comprising the following steps: (1) Clean and level the inner wall surface of the water diversion tunnel, and remove all loose objects and sharp protrusions; (2) A layer of curing polymer waterproof coating is evenly sprayed onto the cleaned inner wall surface of the tunnel to form a continuous waterproof membrane; (3) After the first layer of waterproof membrane has cured, a layer of composite waterproof felt is laid on the surface of the waterproof membrane; (4) Coat the outside of the impermeable felt layer with a layer of self-healing grouting material; (5) Use infrared heating equipment to heat the construction area. The heating temperature is 50~70℃ and the heating time is not less than 2 hours. (6) Conduct an airtightness test on the water diversion tunnel after the heat treatment is completed. Inject compressed air into the tunnel and maintain a predetermined pressure. Verify the seepage prevention effect by observing pressure changes and manually inspecting the surface for signs of leakage.

[0006] Furthermore, in step (1), a quantitative inspection step is added during the cleaning and leveling process. The quantitative inspection process is as follows: (1.1) The surface height field was obtained by laser scanning, and the arithmetic mean roughness was measured by a surface roughness meter. The density of loose particles per unit area was obtained using the vacuum sampling and counting method. The surface moisture content was measured using a capacitive moisture meter. Define surface preparation quality indicators The calculation formula is: ; In the above formula, This indicates the acceptable maximum number of particles. Indicates the maximum height of the remaining protrusion. This indicates the predetermined elimination height reference value. Indicates surface moisture content. Indicates the maximum permissible moisture content. This represents the target roughness set for subsequent coating adhesion optimization, with a weighting coefficient. ; (1.2) When If the surface preparation is deemed satisfactory, then reinforcement is performed according to the adaptive grinding rounds model based on the insufficient rate. The required number of grinding rounds is defined as follows: ; In the above formula, The target pass value is 0.95. This is the current calculated value. The length of the tunnel to be processed. This is the average processing volume coefficient per unit length, used to map the insufficiency rate to workload. The effective processing capacity of a single grinding or cleaning device is rounded up to the nearest integer. (1.3) Perform pull-out bond tests at the preset key locations to ensure the pull-out strength of the substrate. Greater than the thickness of the subsequent waterproof coating and curing temperature Determined minimum adhesion value .

[0007] Furthermore, in step (2), before the spraying step begins, the surface preparation quality index obtained in step (1) is used. and substrate pull-out strength As a standard, only when and The spraying operation will only begin at this time; The sprayed material is a two-component polymer with an optimized low-temperature curing formula. The ratio of the main agent to the curing agent is adjusted in real time according to the site temperature and altitude to maintain a constant viscosity. and constant curing activity ; Introducing a curing time correction model, the on-site surface drying curing time is defined as: ; in, This refers to the surface drying time in seconds. For material constants, The altitude influence coefficient. This refers to the actual altitude in meters. For reference altitude calibration values, For temperature sensitivity coefficient, The absolute temperature of the site is the Kelvin value. The reference temperature is the Kelvin value; Spray coating thickness control according to target thickness For coating thicknesses between 2.0 mm and 3.0 mm, a multi-layer, thin-layer deposition strategy is employed, with the coating machine achieving the nominal deposition thickness per coat as specified by the equipment. Execute and combine the overlap coefficient Calculate the required number of passes, defined as: ; In the above formula, The number of coats is rounded up. Spray transfer efficiency represents the effective deposition ratio from the spray gun to the substrate. The nominal deposition thickness per pass. The overlap ratio between adjacent tracks; During the spraying process, the curing time is monitored in parallel. Adjust the rest time between each repetition; After completing the specified number of coats and passing online thickness and adhesion sampling inspections to meet the standards, a preliminary curing inspection is conducted before proceeding to the subsequent process of laying flexible composite geotextile, ensuring that the coating surface meets the physical and chemical conditions required for the mechanical fixation of the composite felt.

[0008] Furthermore, in step (3), after the first layer of waterproof membrane has been cured and passed the thickness and adhesion sampling inspection, the flexible composite waterproof felt is laid immediately. Before laying, a non-destructive adhesion tester is used to retest the substrate adhesion strength at several marker points. With surface preparation quality indicators The composite felt remains unchanged, unrolled along the roll direction and laid at a certain angle to the tunnel axis along the fiber direction. During laying, a zone tension controller is used to apply a constant pretension to the felt body. Initial displacement constraint is achieved using a mechanical fixation system primarily composed of suture tape and stainless steel spikes. The minimum spacing of the mechanical fixation is calculated based on load balance design, and the unit area of ​​local expansion pressure is defined. And take the effective width of the felt With the bearing shear force of a single anchor The maximum allowable anchorage spacing is... The expression is: ; When measured during actual construction The anchoring density must be increased until After mechanical fixing is completed, peel bond test and anchor pull-out test are carried out in several representative units to verify that the single-point bond strength and anchor shear strength meet the design value and the quality index of step (1). and tensile strength To maintain consistency, after all random inspections are passed, the felt sheets are seamed according to the established overlap rules and based on the fiber modulus. and interfacial shear strength Calculate the minimum overlap length of the joint To ensure that the stress at the joint can be transferred through interfacial bonding and the seam tape during long-term freeze-thaw cycles, the expression for the joint overlap length is: ; in, The parameters are the target coating thickness controlled in step (2) and directly correspond to the interface constraints at the joint. To ensure a safety factor is designed and set at no less than 1.3 in the construction documents, the parameters... To improve the efficiency of interface clipping and transfer; After the laying and fixing are completed and the joints and anchorages are confirmed to meet the design requirements through random inspection, the injection process of external self-healing grouting material is carried out.

[0009] Furthermore, in step (4), after completing the laying and joint fixing of the waterproofing felt and confirming the joint overlap length... Once the design requirements are met, the self-healing grouting material is injected. The grouting system employs a constant pressure and constant flow combined control method and is implemented in zones according to grouting sections. Key quantities monitored in real time on-site include injection pressure. Grouting flow rate Dynamic viscosity of grouting material and the effective permeability of the complex Define the penetration time formula used to calculate the required grouting duration: ; in, The duration of grouting is in seconds. The effective porosity of the composite layer, To achieve the ideal average injection depth; Introducing a healing coverage model to evaluate the repair efficacy of microcapsules and provide decision support for grout formulation: ; in, This represents the desired healing coverage rate within a unit depth. This indicates the effective volume fraction of microcapsules in the grouting material. The actual sealing efficiency coefficient after the microcapsules rupture and release the repair agent; During the grouting process, a method of first low-pressure pre-pumping and then uniformly increasing the pressure to set the working pressure is adopted, and the return ratio and surface seepage recovery rate are recorded simultaneously in each grouting section. After grouting is completed and according to During the period of pressure cessation and curing while waiting for the microcapsules to enter standby mode, several sampling ports should be maintained, and sampling should be conducted on an average scale in the grouting section. After the preset value is reached, the pressure reduction test and pore back pressure test are carried out. After all the tests are confirmed to be qualified, infrared heating is used to uniformly heat the construction area.

[0010] Furthermore, in step (5), before starting infrared heating, the surface drying curing time in step (2) is first set. The target coating thickness in step (3) The required heating energy is fed into the heating energy dispatch model to quantify the required heating energy and guide the heater layout, defining the necessary heat per unit area. The sum of the material's heat capacity and steady-state loss is expressed as: ; In the above formula, The equivalent density of the composite layer, For equivalent specific heat capacity, The equivalent heat capacity thickness is controlled by the steps described above. The thickness is obtained by linear superposition with the effective thickness of the composite waterproof felt. The target heating temperature in this process will be within the range of 50~70℃ and will be calculated in absolute temperature. The initial surface temperature at the start of construction. is the ambient temperature, is the heat loss coefficient per unit area per unit time, is the heating duration; Define the temperature uniformity index as the ratio of the standard deviation of the regional temperature to the temperature scale, and the expression is: ; and use to represent the heating gradient, is the standard deviation of the temperature of several hot spots in the construction area.

[0011] Furthermore, in step (6), after completing heating and curing and determining the interlayer bond strength and the healing coverage rate , start the airtightness test. Use adjustable compressed air to rise to the initial inspection pressure according to the work section and partition and record the duration after stabilizing the pressure and the corresponding pressure . Substitute the recorded values into the pressure decay index for quantitative evaluation. Define the pressure decay index as: ; Introduce the allowable decay upper limit as the qualified judgment threshold, and its expression is: <oo00174>; Among them, and are calibration constants based on material and on-site calibration. The construction judgment rule is that if the measured and there is no record of active seepage in manual inspection and infrared scanning, it is considered that the airtightness is qualified and all the time series data pressure curves and sampling test results are recorded. If any item is unqualified, the specified section shall be repaired by grouting spot welding or local reheating treatment according to the positioning result, and the airtightness test shall be repeated until it meets .

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By introducing a temperature compensation mechanism in a high-altitude environment, a material curing control technology under low pressure, and a dynamic monitoring system for environmental parameters, the present invention enables the anti-seepage construction process to be stably adapted to complex conditions such as high altitude, low temperature, and low pressure, effectively avoiding problems such as cracking, voiding, and leakage that occur in the traditional process in high-altitude areas, and greatly improving the overall construction quality and reliability;<00001B3>(2) The present invention adopts a multi-component composite anti-seepage material system, combined with surface pretreatment, deep grouting, interface reinforcement coating and other technologies, so that the anti-seepage layer and the surrounding rock form a high-strength bonding interface, and improves the structural density through "zone grouting-segment reinforcement-secondary sealing", thereby achieving a long-term anti-seepage effect with high strength, high toughness, freeze-thaw resistance and water pressure impact resistance; (3) The present invention deploys multiple monitoring devices such as displacement sensors, pore water pressure gauges, and ultrasonic compaction testers to build a real-time data acquisition and intelligent construction control platform. Through the working condition analysis model, key parameters such as grouting volume, pressure, and rate are automatically calibrated, which greatly reduces the reliance on manual experience and realizes the visualization, precision, and controllability of the construction process, effectively reducing the rework rate and improving work efficiency. (4) This invention is designed for geological environments such as high ground stress, weak interlayers, and fault fracture zones. The solution adopts the strategy of "advanced detection + adjustable support + integrated treatment of seepage prevention and reinforcement". By dynamically adjusting the grouting diffusion range, support parameters and seepage prevention thickness, it effectively suppresses adverse factors such as surrounding rock deformation and seepage pressure rise, improves the overall stability of the tunnel, and significantly improves the construction safety of poor sections. (5) By constructing a long-term structural health monitoring mechanism, this invention periodically assesses the deformation, seepage pressure, water flow changes and material status of the seepage barrier layer, thereby achieving early warning and precise maintenance. At the same time, the improved durability of the seepage barrier structure significantly reduces the frequency of later repairs, thereby significantly reducing the operation and maintenance costs of the water diversion tunnel of the high-altitude hydropower station and effectively extending the overall life cycle. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating step (1) of the construction method described in this invention; Figure 2 This is a flowchart illustrating step (2) of the construction method described in this invention; Figure 3 This is a flowchart illustrating step (3) of the construction method described in this invention; Figure 4 This is a flowchart illustrating step (4) of the construction method described in this invention; Figure 5 This is a flowchart illustrating step (5) of the construction method described in this invention. Detailed Implementation

[0014] The present invention will be further described below with reference to specific embodiments.

[0015] The seepage prevention construction method for water diversion tunnels in high-altitude hydropower stations according to the present invention includes the following steps: (1) such as Figure 1As shown, the inner wall surface of the water diversion tunnel is cleaned and leveled to remove all loose material and sharp protrusions, ensuring the surface is clean and dry, providing an ideal base for the subsequent construction of the seepage prevention layer.

[0016] In this step, quantitative testing is also incorporated into the construction process to avoid potential problems caused by subjective judgment. Specifically: (1.1) First, the surface height field was obtained by high-resolution laser scanning, and the arithmetic mean roughness was measured by a portable surface roughness meter. The density of loose particles per unit area was obtained using the vacuum sampling and counting method. The surface moisture content was measured using a capacitive moisture meter. Define surface preparation quality indicators The calculation formula is: ; In the above formula, This indicates the acceptable maximum number of particles. Indicates the maximum height of the remaining protrusion. This indicates the predetermined elimination height reference value. Indicates surface moisture content. Indicates the maximum permissible moisture content. This represents the target roughness set for subsequent coating adhesion optimization, with a weighting coefficient. To reflect the importance of different factors, the actual effect of this indicator is that it can unify discrete detection values ​​onto a scale of 0 to 1, which facilitates comparison and closed-loop control.

[0017] (1.2) When If the surface preparation is deemed satisfactory, then reinforcement is performed according to the adaptive grinding rounds model based on the insufficient rate. The required number of grinding rounds is defined as follows: ; In the above formula, The target pass value is 0.95. This is the current calculated value. The length of the tunnel to be processed. This is the average processing volume coefficient per unit length, used to map the insufficiency rate to workload. The effective processing capacity of a single grinding or cleaning operation is represented by an integer rounding sign to ensure that the number of process rounds is an integer. The purpose of the first algorithm is to quantify quality defects into the number of executable mechanical operations and directly couple them with equipment energy efficiency to optimize resource allocation.

[0018] (1.3) Perform pull-out bond tests at several key locations to ensure the pull-out strength of the substrate. Greater than the thickness of the subsequent waterproof coating and curing temperature Determined minimum adhesion value This test ensures that the subsequent low-temperature curing polymer coating can achieve the designed adhesion within the set thickness range. All tests can proceed to step (2) only after the requirements are met.

[0019] (2) For example Figure 2 As shown, a layer of low-temperature curing polymer waterproof coating is uniformly sprayed onto the cleaned inner wall surface of the tunnel. Low temperature refers to 0℃ to -10℃. This coating can quickly cure to form a continuous waterproof membrane in high-altitude and low-temperature environments. The spray thickness is controlled between 2 and 3 mm. Automated spraying equipment can be used to ensure the uniformity of the coating.

[0020] Before the spraying step begins, the surface preparation quality indicators obtained in step (1) must be used. and substrate pull-out strength As a standard, only when and The spraying operation will only begin at this time; The sprayed material is a two-component polymer with an optimized low-temperature curing formula. The ratio of the main agent to the curing agent is adjusted in real time according to the site temperature and altitude to maintain a constant viscosity. and constant curing activity ; To address the changes in atomization and volatilization caused by high altitude and low pressure, a curing time correction model is introduced to ensure continuous film formation. The on-site surface drying curing time is defined as: ; in, This refers to the surface drying time in seconds. For material constants, The altitude influence coefficient is used to characterize the trend of solidification extension with increasing altitude. This refers to the actual altitude in meters. For reference altitude calibration values, The temperature sensitivity coefficient is used to characterize the effect of ambient temperature on the curing rate. The absolute temperature of the site is the Kelvin value. The reference temperature is Kelvin. The purpose of this formula is to incorporate the coupling of altitude and temperature on the curing rate into the automatic spraying controller in a calculable way, so that the spraying rate is matched in a closed loop with the gun speed, feed rate and inter-layer pause time, ensuring the formation of a continuous pinhole-free film within the target thickness range.

[0021] Spray coating thickness control according to target thickness For coating thicknesses between 2.0 mm and 3.0 mm, a multi-layer, thin-layer deposition strategy is employed, with the coating machine achieving the nominal deposition thickness per coat as specified by the equipment. Execute and combine the overlap coefficient Calculate the required number of passes, defined as: ; In the above formula, The number of coats is rounded up. Spray transfer efficiency represents the effective deposition ratio from the spray gun to the substrate. The nominal deposition thickness per pass. This represents the overlap ratio between adjacent rails. This formula couples the geometric parameters of the spraying equipment and the on-site deposition efficiency into the number of feasible passes. When the thickness uniformity requirement is met, a portable ultrasonic thickness gauge or dry film thickness gauge is used to obtain the real-time thickness distribution at several uniform sampling points. The error is then fed back to the spray gun movement speed and discharge flow rate to achieve closed-loop correction.

[0022] During the spraying process, the curing time is monitored in parallel. Adjusting the pause time between each pass and, if necessary, using low-power infrared preheating in localized areas to shorten localized surface drying time can prevent sagging or insufficient interlayer adhesion in the next coating pass.

[0023] After completing the specified number of coats and passing online thickness and adhesion sampling inspections to meet the standards, a preliminary curing inspection is conducted before proceeding to the subsequent process of laying flexible composite geotextile, ensuring that the coating surface meets the physical and chemical conditions required for the mechanical fixation of the composite felt.

[0024] (3) such as Figure 3 As shown, after the first layer of waterproof membrane has cured, a layer of flexible composite anti-seepage felt is laid on the surface of the waterproof membrane. The anti-seepage felt is made of polymer fibers and inorganic materials, and has high elasticity and anti-freeze-swell properties. It is tightly attached to the surface of the waterproof membrane by mechanical fixing.

[0025] It is important to note that the flexible composite waterproofing felt should be laid immediately after the first layer of waterproofing membrane has cured and passed thickness and adhesion tests. Before laying, the adhesion strength of the substrate should be retested at several marker points using a non-destructive adhesion tester. With surface preparation quality indicators To ensure the bonding surface meets mechanical fixing requirements, the composite felt is unrolled in the roll direction and laid at a certain angle to the tunnel axis along the fiber direction to improve the stress dispersion ability in the circumferential and axial directions. During laying, a zoned tension controller is used to apply a constant pretension to the felt body. Initial fixation displacement is constrained using a mechanical fastening system primarily composed of suture tape and stainless steel spikes. The minimum spacing of the mechanical fasteners is calculated based on load balance design to resist the radial expansion force of the composite felt during freeze-thaw expansion and the additional shear that may occur after construction. The unit area of ​​local expansion pressure is defined. And take the effective width of the felt With the bearing shear force of a single anchor The maximum allowable anchorage spacing is... The expression is: ; The purpose of this formula is to couple the material’s resistance to frost heave into the anchorage layout in the form of engineering loads, thereby directly providing an executable spacing value.

[0026] When measured during actual construction The anchoring density must be increased until After mechanical fixing is completed, peel bond test and anchor pull-out test are carried out in several representative units to verify that the single-point bond strength and anchor shear strength meet the design value and the quality index of step (1). and tensile strength To maintain consistency, after all random inspections are passed, the felt sheets are seamed according to the established overlap rules and based on the fiber modulus. and interfacial shear strength Calculate the minimum overlap length of the joint To ensure that the stress at the joint can be transferred through interfacial bonding and the seam tape during long-term freeze-thaw cycles, the expression for the joint overlap length is: ; in, The parameters are the target coating thickness controlled in step (2) and directly correspond to the interface constraints at the joint. To ensure a safety factor is designed and set at no less than 1.3 in the construction documents, the parameters... To improve the efficiency of interfacial shear transfer, this overlap length calculation couples the mechanical properties of the felt with the coating thickness, thereby maintaining the mechanical integrity of the overall seepage prevention system during subsequent freeze-thaw and grouting stages. After the laying and fixing are completed and the joints and anchorages are confirmed to meet the design requirements through random inspection, the injection process of external self-healing grouting material is initiated.

[0027] (4) such as Figure 4 As shown, a self-healing grouting material is coated on the outside of the impermeable felt layer. This material can be a polyurethane-based grouting material containing epoxy resin microcapsules or a cement-based composite grouting material containing polyurethane microcapsules. It contains microcapsule repair agents. When micro-cracks occur, the microcapsules rupture and release repair substances to automatically seal the leakage points. The grouting pressure is controlled at 0.5~1 MPa to ensure that the material fully penetrates.

[0028] After completing the laying and joint fixing of the impermeable felt, and confirming the overlap length of the joints. Once the design requirements are met, the self-healing grouting material is injected. The grouting process ensures that the material can penetrate into the microcracks between the composite felt and the underlying coating and that the microcapsules are distributed to achieve the desired healing coverage rate.

[0029] The grouting system employs a constant pressure and constant flow combined control method and is implemented in zones according to grouting sections. Key quantities monitored in real time on-site include injection pressure. Grouting flow rate Dynamic viscosity of grouting material and the effective permeability of the complex These amounts should be consistent with the target coating thickness controlled in step (2). The overlap length of the seam determined in step (3) This is incorporated into the grouting parameter table to ensure interlayer continuity. To quantify qualitative permeability targets and guide grouting duration, a permeability time formula is defined to calculate the required grouting duration: ; in, The duration of grouting is in seconds. The effective porosity of the composite layer, For the ideal average injection depth, this depth should cover at least half the thickness from the outer surface of the geotextile to the coating neutralization interface, thus... A direct response occurred. This is the equivalent permeability of the composite layer under grouting pressure conditions, which can be obtained through field tests. The dynamic viscosity of the grouting material at the on-site temperature is maintained within the injectable range by a formula adjuster. To control the injection overpressure and maintain it in the range of 0.5 to 1 MPa in each grouting segment, the purpose of this formula is to couple the pore structure viscosity and permeability with the injection pressure into a calculable grouting period, thereby avoiding over-injection leading to material backflow or under-injection leading to insufficient coverage.

[0030] Introducing a healing coverage model to evaluate the repair efficacy of microcapsules and provide decision support for grout formulation: ; in, This represents the desired healing coverage rate within a unit depth. This indicates the effective volume fraction of microcapsules in the grouting material. The coefficient representing the actual sealing efficiency after microcapsule rupture and release of the repair agent is determined by indoor aging tests and small-scale field crack release tests. The model maps the product of microcapsule concentration and injection depth to a sealing probability, thus enabling quantitative design of the grouting formulation. Grouting operations employ a low-pressure pre-pumping followed by a uniform pressurization to the set working pressure. The backflow ratio and surface seepage recovery rate are recorded simultaneously at each grouting section to determine if channelization along the bedding plane occurs. When the backflow ratio exceeds the warning threshold, the injection rate is immediately reduced, and alternating sealing and backpressure treatments are implemented along the grouting holes to promote material redistribution.

[0031] After grouting is completed and according to During the period of pressure cessation and curing while waiting for the microcapsules to enter standby mode, several sampling ports should be retained for post-curing microscopic inspection and healing tests, and the average sampling should be conducted in the grouting section. After reaching the preset value, pressure reduction test and pore back pressure test are carried out to confirm that there is no abnormal backflow and no continuous seepage. After all are confirmed to be qualified, infrared heating is used to uniformly heat the construction area to promote interlayer fusion and overall curing in the next process.

[0032] (5) such as Figure 5 As shown, infrared heating equipment is used to heat the construction area to promote the fusion and overall curing of each impermeable layer. The heating temperature is 50~70℃ and the heating time is not less than 2 hours to enhance the interlayer adhesion and structural integrity.

[0033] Before starting infrared heating, first determine the surface drying time in step (2). The target coating thickness in step (3) The required heating energy is fed into the heating energy dispatch model to quantify the required heating energy and guide the heater layout, defining the necessary heat per unit area. The sum of the material's heat capacity and steady-state loss is expressed as: ; In the above formula, The equivalent density of the composite layer, For equivalent specific heat capacity, The equivalent heat capacity thickness is controlled by the steps described above. The thickness is obtained by linear superposition with the effective thickness of the composite waterproof felt. The target heating temperature in this process will be within the range of 50~70℃ and will be calculated in absolute temperature. The initial surface temperature at the start of construction. For ambient temperature, The heat loss coefficient per unit time and per unit area. The purpose of this energy formula for heating duration is to couple the thermal properties of the material with the environmental losses in the field into a controllable energy input, thereby meeting the minimum heating duration requirements while avoiding overheating that could lead to premature rupture of microcapsules or excessive stress on the coating.

[0034] To ensure heating uniformity and guide the placement and power distribution of infrared devices with engineering quantification indicators, a temperature uniformity index is defined. The ratio of the regional temperature standard deviation to the temperature scale is expressed as: ; and use Indicates the heating gradient. This represents the standard deviation of temperature at several hot spots within the construction area. The construction control objective is... This is to ensure that local temperature differences do not lead to an increase in interlayer adhesion gradient or microcapsule failure probability.

[0035] Actual control is achieved through closed-loop feedback, with the infrared emitting array controller using thermal imaging sensors and spot temperature probes for synchronous sampling. With the regional average temperature and according to the energy formula With uniformity index Jointly adjust the transmission power of each unit until Stabilize and maintain the temperature for at least 2 hours while monitoring key temperature thresholds to avoid exceeding the microcapsule's temperature resistance limit and the polymer's thermal degradation curve. After heating, gradually cool according to the thermal annealing curve and repeat the measurements at the thermal imaging and adhesion test points. To verify that the interlayer bonding improvement effect meets expectations, all data are recorded in the construction report and used as benchmark data for subsequent airtightness testing before proceeding to the next step for airtightness testing.

[0036] (6) Conduct an air tightness test on the water diversion tunnel after the heat treatment is completed. Inject compressed air into the tunnel and maintain the predetermined pressure. Verify the seepage prevention effect by observing the pressure change and manually inspecting the surface for signs of leakage. After the test is qualified, the construction is completed.

[0037] Complete the aforementioned heating and curing process and confirm interlayer adhesion. With healing coverage Then, the airtightness test was initiated, and the pressure was slowly increased to the initial test pressure using adjustable compressed air, divided into sections. The duration was recorded after voltage stabilization. Corresponding pressure The recorded values ​​are substituted into the pressure decay index for quantitative assessment. The pressure decay index is defined as follows: ; The purpose of this indicator is to characterize the overall leakage rate of the system using a time-normalized logarithmic decay rate, thus reflecting the overall leakage more accurately than single-point observations and being comparable to previous grouting coverage. Interlayer adhesion Direct comparison. The test was conducted in conjunction with manual inspection and infrared thermal imaging to locate abnormal points of surface temperature difference and micro-seepage traces. At each abnormal point, the local back pressure curve and reflux ratio were recorded to determine whether there was a channelized penetration path.

[0038] To quantify performance indicators and design requirements, an upper limit for allowable attenuation is introduced. As a threshold for qualification, this threshold is determined by the healing coverage rate. Interlayer adhesion Heating uniformity index With the target coating thickness Joint decision, the expression of which is: ; where and are calibration constants based on material and on-site calibration. The design intention is that the higher the healing coverage rate, the greater the interfacial bonding force, and the lower the allowable attenuation rate when the temperature uniformity is better, so as to strictly restrict the existence of micro-leakage. The construction judgment rule is that if is measured and there is no record of active seepage in manual inspection and infrared scanning, it is determined that the airtightness is qualified and all timing data pressure curves and sampling test results are recorded. If any item is unqualified, the designated section is subjected to supplementary grouting, spot welding reinforcement or local reheating treatment according to the positioning results, and the airtightness test is repeated until is satisfied, and the final acceptance and construction record filing are completed.

Claims

1. A method for seepage prevention construction of a water diversion tunnel for a high-altitude hydropower station, characterized in that, The method includes the following steps: (1) Clean and level the inner wall surface of the water diversion tunnel, and remove all loose objects and sharp protrusions; (2) A layer of curing polymer waterproof coating is evenly sprayed onto the cleaned inner wall surface of the tunnel to form a continuous waterproof membrane; (3) After the first layer of waterproof membrane has cured, a layer of composite waterproof felt is laid on the surface of the waterproof membrane; (4) Coat the outside of the impermeable felt layer with a layer of self-healing grouting material; (5) Use infrared heating equipment to heat the construction area. The heating temperature is 50~70℃ and the heating time is not less than 2 hours. (6) Conduct an airtightness test on the water diversion tunnel after the heat treatment is completed. Inject compressed air into the tunnel and maintain a predetermined pressure. Verify the seepage prevention effect by observing pressure changes and manually inspecting the surface for signs of leakage.

2. The seepage prevention construction method for water diversion tunnels in high-altitude hydropower stations according to claim 1, characterized in that, In step (1), a quantitative inspection step is added during the cleaning and leveling process. The quantitative inspection process is as follows: (1.1) The height field of the inner wall surface of the water diversion tunnel was obtained by laser scanning, and the arithmetic mean roughness was measured by a surface roughness meter. The density of loose particles per unit area on the inner wall surface of the water diversion tunnel was obtained using the vacuum sampling and counting method. The moisture content of the inner wall surface of the water diversion tunnel was measured using a capacitive moisture meter. Define surface preparation quality indicators The calculation formula is: ； In the above formula, This indicates the acceptable maximum number of particles. Indicates the maximum height of the remaining protrusion. This indicates the predetermined elimination height reference value. Indicates surface moisture content. Indicates the maximum permissible moisture content. This represents the target roughness set for subsequent coating adhesion optimization, with a weighting coefficient. ; (1.2) When If the surface preparation is deemed satisfactory, then reinforcement is performed according to the adaptive grinding rounds model based on the insufficient rate. The required number of grinding rounds is defined as follows: ； In the above formula, The target pass value is 0.

95. This is the current calculated value. The length of the tunnel to be processed. This is the average processing volume coefficient per unit length, used to map the insufficiency rate to workload. The effective processing capacity of a single grinding or cleaning device is rounded up to the nearest integer. (1.3) Perform pull-out bond tests at the preset key locations to ensure the pull-out strength of the substrate. Greater than the thickness of the subsequent waterproof coating and curing temperature Determined minimum adhesion value .

3. The seepage prevention construction method for water diversion tunnels in high-altitude hydropower stations according to claim 2, characterized in that, In step (2), before the spraying step begins, the surface preparation quality index obtained in step (1) is used. and substrate pull-out strength As a standard, only when and The spraying operation will only begin at this time; The sprayed material is a two-component polymer with an optimized low-temperature curing formula. The ratio of the main agent to the curing agent is adjusted in real time according to the site temperature and altitude to maintain a constant viscosity. and constant curing activity ; Introducing a curing time correction model, the on-site surface drying curing time is defined as: ； in, This refers to the surface drying time in seconds. For material constants, The altitude influence coefficient. This refers to the actual altitude in meters. For reference altitude calibration values, For temperature sensitivity coefficient, The absolute temperature of the site is the Kelvin value. The reference temperature is the Kelvin value; Spray coating thickness control according to target thickness For coating thicknesses between 2.0 mm and 3.0 mm, a multi-layer, thin-layer deposition strategy is employed, with the coating machine achieving the nominal deposition thickness per coat as specified by the equipment. Execute and combine the overlap coefficient Calculate the required number of passes, defined as: ； In the above formula, The number of coats is rounded up. Spray transfer efficiency represents the effective deposition ratio from the spray gun to the substrate. The nominal deposition thickness per pass. The overlap ratio between adjacent tracks; During the spraying process, the curing time is monitored in parallel. Adjust the rest time between each repetition; After completing the specified number of coats and passing online thickness and adhesion sampling inspections to meet the standards, a preliminary curing inspection is conducted before proceeding to the subsequent process of laying flexible composite geotextile, ensuring that the coating surface meets the physical and chemical conditions required for the mechanical fixation of the composite felt.

4. The seepage prevention construction method for water diversion tunnels in high-altitude hydropower stations according to claim 3, characterized in that, In step (3), the flexible composite waterproofing felt is laid immediately after the first layer of waterproof membrane has cured and passed the thickness and adhesion inspection. Before laying, the adhesion strength of the substrate is retested at several marker points using a non-destructive adhesion tester. With surface preparation quality indicators The composite felt remains unchanged, unrolled along the roll direction and laid at a certain angle to the tunnel axis along the fiber direction. During laying, a zone tension controller is used to apply a constant pretension to the felt body. Initial displacement constraint is achieved using a mechanical fixation system primarily composed of suture tape and stainless steel spikes. The minimum spacing of the mechanical fixation is calculated based on load balance design, and the unit area of ​​local expansion pressure is defined. And take the effective width of the felt With the bearing shear force of a single anchor The maximum allowable anchorage spacing is... The expression is: ； When measured during actual construction The anchoring density must be increased until After mechanical fixing is completed, peel bond test and anchor pull-out test are carried out in several representative units to verify that the single-point bond strength and anchor shear strength meet the design value and the quality index of step (1). and tensile strength To maintain consistency, after all random inspections are passed, the felt sheets are seamed according to the established overlap rules and based on the fiber modulus. and interfacial shear strength Calculate the minimum overlap length of the joint To ensure that the stress at the joint can be transferred through interfacial bonding and the seam tape during long-term freeze-thaw cycles, the expression for the joint overlap length is: ； in, The parameters are the target coating thickness controlled in step (2) and directly correspond to the interface constraints at the joint. To ensure a safety factor is designed and set at no less than 1.3 in the construction documents, the parameters... To improve the efficiency of interface clipping and transfer; After the laying and fixing are completed and the joints and anchorages are confirmed to meet the design requirements through random inspection, the injection process of external self-healing grouting material is carried out.

5. The seepage prevention construction method for water diversion tunnels in high-altitude hydropower stations according to claim 4, characterized in that, In step (4), after the laying of the waterproofing felt and the joint fixing are completed, the overlap length of the joints is confirmed. Once the design requirements are met, the self-healing grouting material is injected. The grouting system employs a constant pressure and constant flow combined control method and is implemented in zones according to grouting sections. Key quantities monitored in real time on-site include injection pressure. Grouting flow rate Dynamic viscosity of grouting material and the effective permeability of the complex Define the penetration time formula used to calculate the required grouting duration: ； in, The duration of grouting is in seconds. The effective porosity of the composite layer, To achieve the ideal average injection depth; Introducing a healing coverage model to evaluate the repair efficacy of microcapsules and provide decision support for grout formulation: ； in, This represents the desired healing coverage rate within a unit depth. This indicates the effective volume fraction of microcapsules in the grouting material. The actual sealing efficiency coefficient after the microcapsules rupture and release the repair agent; During the grouting process, a method of first low-pressure pre-pumping and then uniformly increasing the pressure to set the working pressure is adopted, and the return ratio and surface seepage recovery rate are recorded simultaneously in each grouting section. After grouting is completed and according to During the period of pressure cessation and curing while waiting for the microcapsules to enter standby mode, several sampling ports should be maintained, and sampling should be conducted on an average scale in the grouting section. After the preset value is reached, the pressure reduction test and pore back pressure test are carried out. After all the tests are confirmed to be qualified, infrared heating is used to uniformly heat the construction area.

6. The seepage prevention construction method for water diversion tunnels in high-altitude hydropower stations according to claim 5, characterized in that, In step (5), before starting infrared heating, the surface drying time in step (2) is first set. The target coating thickness in step (3) The required heating energy is fed into the heating energy dispatch model to quantify the required heating energy and guide the heater layout, defining the necessary heat per unit area. The sum of the material's heat capacity and steady-state loss is expressed as: ； In the above formula, The equivalent density of the composite layer, For equivalent specific heat capacity, The equivalent heat capacity thickness is controlled by the steps described above. The thickness is obtained by linear superposition with the effective thickness of the composite waterproof felt. The target heating temperature in this process will be within the range of 50~70℃ and will be calculated in absolute temperature. The initial surface temperature at the start of construction. For ambient temperature, The heat loss coefficient per unit time and per unit area. This refers to the heating duration. Define temperature uniformity index The ratio of the regional temperature standard deviation to the temperature scale is expressed as: ； and use Indicates the heating gradient. The standard deviation of temperature for several hot spots within the construction area.

7. The seepage prevention construction method for water diversion tunnels in high-altitude hydropower stations according to claim 6, characterized in that, In step (6), after heating and curing are completed and the interlayer adhesion is determined... With healing coverage Then, the airtightness test was initiated, and adjustable compressed air was used to raise the pressure to the initial test pressure according to the work section. The duration was recorded after voltage stabilization. Corresponding pressure The recorded values ​​are substituted into the pressure decay index for quantitative assessment. The pressure decay index is defined as follows: ； Introduce an upper limit on allowable decay As the qualification threshold, its expression is: ； Among them, and are calibration constants based on material and on-site calibration. The construction judgment rule is that if is measured and there is no record of active seepage in manual inspection and infrared scanning, the airtightness is considered qualified and all time-series data pressure curves and sampling test results are recorded. If any item is unqualified, grouting spot welding reinforcement or local reheating treatment is carried out on the specified section according to the positioning result, and the airtightness test is repeated until .

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