A type of water conveyance tunnel lining

Abstract

This invention relates to the field of hydraulic tunnel lining structure technology, and discloses a water conveyance tunnel lining, including an outer bearing layer, an inner bearing layer, and a thickened fluid interlayer sandwiched between the two bearing layers and filled with a shear-thickened fluid. The shear-thickened fluid can change its viscosity with changes in pressure inside and outside the tunnel and solidify under impact. This invention relies on the double bearing layer combined with the thickened fluid interlayer with adaptive rheological properties to passively achieve adaptive adjustment of lining stiffness without external auxiliary equipment. It can release stress through flexible buffering under static loads and instantly solidify under impact loads to improve overall stiffness, simultaneously adapting to various working conditions, reducing the probability of lining cracking, reducing project costs, and the entire structure is simple and long-lasting.

Description

Technical Field

[0001] This invention relates to the field of hydraulic tunnel technology, specifically to a water conveyance tunnel lining. Background Technology

[0002] Long-distance water conveyance tunnels operate under complex conditions. During normal water conveyance, they are subjected to stable internal water pressure, while during the water outage and emptying phase, they are subjected to external pressure from the surrounding rock and groundwater. The start-up and shutdown of pump stations and the opening and closing of valves will also generate instantaneous water hammer impact loads. The existing conventional water conveyance tunnel linings are all integral rigid concrete structures with fixed stiffness, which cannot adapt to the changing load conditions.

[0003] Furthermore, rigid linings lack structural space to buffer deformation. The deformation of the surrounding rock and temperature stress caused by slow static loads will directly act on the lining body, which is prone to cracking. The instantaneous impact pressure peak caused by water hammer is borne entirely by the lining alone. After repeated impacts, the lining is very prone to cracking and damage. If the reinforcement of the lining is uniformly thickened to resist the peak load of water hammer, it will significantly increase the overall cost of the project. Summary of the Invention

[0004] This invention provides a water conveyance tunnel lining to solve the problems of high engineering cost and poor impact protection effect caused by the inability of the lining to adapt to the variable load conditions such as static pressure and instantaneous water hammer impact of the tunnel.

[0005] This invention provides a water conveyance tunnel lining, comprising: The outer bearing layer is used to withstand the external pressure of the tunnel; An inner bearing layer is disposed inside the outer bearing layer and is used to withstand the internal pressure of the tunnel. A thickened fluid interlayer is disposed between the outer bearing layer and the inner bearing layer, and the thickened fluid interlayer is filled with a shear-thickened fluid. The shear-thickened fluid can change its viscosity when shear force is generated by internal or external pressure in the tunnel, so that the shear-thickened fluid can solidify when subjected to shear force.

[0006] Beneficial Effects: The core layered structure employs a double-layered bearing structure with a thickened fluid interlayer sandwiched between the two layers. The outer bearing layer independently bears the compression load of the tunnel surrounding rock and external pressures such as groundwater seepage pressure, while the inner bearing layer independently resists the internal water pressure from the water transported within the tunnel. The force boundaries of the two bearing layers are clearly defined, and the loads are separated. Compared to the traditional single-layer monolithic concrete lining, which suffers from severe stress concentration due to the concentrated superposition of internal and external loads, the double-layered structure can disperse both internal and external loads, significantly improving the overall load-bearing safety redundancy of the lining. A thickened fluid interlayer is specially set between the two bearing layers, filled with shear-thickened fluid. This shear-thickened fluid can autonomously change its viscosity according to the relative deformation rate of the two bearing layers caused by the external pressure inside the tunnel. Once subjected to instantaneous impact loads, it can quickly solidify and lock the two layers together.

[0007] Under static and slow working conditions such as slow surrounding rock creep, slow venting and maintenance, and slow external pressure loading in long-term stable water conveyance tunnels, the inner and outer bearing layers only undergo low-speed, minute relative displacement. The shear-thickened fluid maintains a low-viscosity, flowable state, allowing for free, small-amplitude sliding between the two layers. The slow deformation of the surrounding rock, the temperature expansion and contraction stress of the concrete, and the additional stress generated by the long-term stable internal and external water pressure can all be completely buffered and released through the flexible flow of the interlayer fluid. The stress is not directly and rigidly transmitted to the concrete body, thus reducing defects such as circumferential and longitudinal penetrating cracks and surface cracking in the lining from the root cause.

[0008] When the pump station's start-stop valves rapidly open and close, generating millisecond-level water hammer impacts that cause a sudden rise and fall in pressure inside the tunnel, the inner and outer bearing layers undergo high-speed relative shearing motion. The viscosity of the shear-thickened fluid in the interlayer increases dramatically and solidifies rapidly, rigidly locking the outer and inner bearing layers, which were originally able to slide relative to each other, into a single unit. The overall stiffness of the lining increases several times in a short period of time, directly offsetting and weakening the instantaneous pressure peak caused by the water hammer, and preventing the impact stress concentration from penetrating the concrete lining.

[0009] The entire structure can adapt to various working conditions, eliminating the need for uniformly thickening the lining reinforcement and increasing the concrete thickness according to extreme peak water hammer loads. This significantly reduces the amount of reinforced concrete used, effectively lowering the overall cost of the tunnel project. Furthermore, the stiffness is passively adjusted entirely by the fluid's own material properties, eliminating the need for external auxiliary equipment such as sensors, electrical control systems, hydraulic pipelines, and pressure regulating valves. This avoids issues like pipeline blockages, electrical malfunctions, and regular valve maintenance. It is suitable for the entire layout of water conveyance tunnels spanning tens of kilometers, simplifying construction procedures and significantly reducing subsequent maintenance workload.

[0010] In one alternative embodiment, the shear-thickened fluid is a nanoparticle suspension.

[0011] Beneficial effects: By limiting the shear-thickened fluid to a nanoparticle suspension, the nanoscale solid particles can be uniformly dispersed and suspended in the liquid medium, exhibiting excellent fluidity. This allows the fluid to completely fill the narrow spaces within the thickened fluid interlayer, preventing the problem of localized areas lacking effective fluid filling due to particle deposition. Simultaneously, the large specific surface area of ​​the nanoparticles allows them to rapidly form a contact network under shear stress, resulting in a viscosity change response speed at the millisecond level. Compared to conventional large-particle thickened fluids, this suspension system is more sensitive to instantaneous impacts, precisely matching the protection requirements against water hammer. Under static low-speed deformation conditions, the fluid flows uniformly, maintaining consistent buffering deformation capacity throughout the interlayer, eliminating any weak points where localized buffering failure occurs.

[0012] In one alternative embodiment, the shear-thickened fluid has a shear rate of less than 10 s. - ¹When the shear-thickened fluid viscosity is less than 5 Pa·s; The shear-thickened fluid has a shear rate greater than 10s. - ¹When the shear-thickened fluid has a viscosity greater than 500 Pa·s.

[0013] Beneficial effects: Under low-speed static deformation conditions, fluid flow resistance is minimal, and slippage between the inner and outer bearing layers is smooth. Minor creep in the surrounding rock, temperature expansion and contraction of the concrete, and slow water pressure deformation can all be fully absorbed by the interlayer, preventing residual additional stress within the lining. As the shear rate increases, the viscosity can increase by hundreds of times. Upon high-speed shear impact, the fluid loses its fluidity, forming a solid bearing medium that firmly restricts the relative displacement of the inner and outer bearing layers, significantly improving the overall impact and deformation resistance of the lining. The two sets of viscosity parameters create a significant performance difference, clearly defining the two independent working states of static buffering and impact reinforcement. The boundary between working conditions is clear, preventing intermediate transitions of insufficient buffering or reinforcement failure, ensuring stable and reliable operation of the lining in both working modes.

[0014] In one alternative embodiment, the shear-thickened fluid comprises a suspension of mixed nanoparticles of nano-silica and polyethylene glycol PEG-400.

[0015] Beneficial effects: Using nano-silica as the solid phase particles results in high particle hardness and strong mechanical stability; even after millions of shear-thickening cycles, the particles will not break down or degrade in performance. Polyethylene glycol (PEG-400) serves as the liquid phase carrier, exhibiting water resistance, high and low temperature resistance, and low volatility. It will not be diluted or lost even after long-term immersion in the humid water environment of tunnels, making it perfectly suited for the permanent underwater service environment of tunnels. The suspension formed by the two compounds exhibits excellent compatibility and will not separate into solid and liquid phases even after long-term static standing at room temperature. Compared to oil-based organic solvent-based thickened fluids, the water-based PEG medium is non-corrosive and will not erode the concrete bearing layers and rubber sealing components on both sides. Long-term use will not damage the main lining structure or sealing system.

[0016] In one alternative embodiment, the shear-thickened fluid further includes ammonium polyacrylate dispersant, fumed silica anti-settling agent, and antioxidant.

[0017] Beneficial effects: Ammonium polyacrylate dispersant can encapsulate nano-silica particles, eliminating electrostatic agglomeration between particles and ensuring long-term uniform dispersion of nanoparticles in the PEG liquid phase. Fumed silica, as an anti-settling agent, enhances the suspension and support capacity of the liquid medium. Even during long-term shutdown and static placement of the tunnel, solid particles will not settle and accumulate at the bottom of the interlayer, ensuring consistent fluid performance throughout the entire interlayer. Antioxidants can delay the oxidative aging of the polyethylene glycol liquid phase, preventing deterioration and failure of the medium under long-term high-temperature underwater conditions, significantly extending the overall service life of the shear-thickened fluid, and reducing maintenance work required for subsequent fluid replenishment and replacement.

[0018] In an optional embodiment, a partition structure is further included, which is disposed within the thickened fluid interlayer for dividing the shear-thickened fluid into partitions. The partition structure includes: Circumferential baffles are arranged along the circumferential direction of the thickened fluid interlayer; Longitudinal partitions are arranged at intervals along the axial direction of the thickened fluid interlayer.

[0019] Beneficial effects: By circumferential baffles arranged around the tunnel circumference and longitudinal baffles arranged at intervals along the tunnel's length, the thickened fluid interlayer of the long tunnel is divided into multiple independent sections through their interlocking arrangement. Without this separating structure, the entire interlayer would be interconnected, and due to the tunnel's slope and long-term unidirectional stress, the fluid would easily shift and accumulate to one end, causing localized fluid shortages and loss of buffering and protective capabilities. This separating structure restricts the fluid's movement range, with a fixed fluid volume within each section. The fluid is evenly distributed throughout the tunnel, and when water hammer occurs at any location, the fluid in the corresponding section can independently undergo shearing and thickening, preventing the weakening of local impact resistance due to large-scale fluid flow and dispersion.

[0020] In one alternative embodiment, the circumferential partition and the longitudinal partition together form a plurality of sealed cavities, and the shear-thickened fluid is contained within the sealed cavities.

[0021] Beneficial effects: The partitions form independent, sealed cavities, confining the shear-thickened fluid within their respective chambers. The fluid is physically isolated, preventing widespread free movement within the interlayer. Each independent cavity can independently withstand the internal and external pressures of its corresponding area. Differences in tunnel loads across different sections do not interfere with each other, avoiding the pressure of high-pressure fluid in localized areas compressing into low-pressure zones and causing overall stress imbalance. Simultaneously, the independent sealing of each cavity means that even a minor leak in a single chamber only affects the fluid in that specific area, preventing the complete loss of fluid throughout the interlayer. The impact of the fault is controllable, and subsequent repairs and fluid injections only require addressing the corresponding cavity, significantly reducing maintenance workload.

[0022] In one optional embodiment, the sealing cavity is provided with a connecting hole at the positions of the circumferential partition and the longitudinal partition to achieve pressure equalization of the shear-thickened fluid.

[0023] Beneficial effects: Adjacent sealed cavities are interconnected through the connecting holes of the partition plates. Under long-term static water supply and venting maintenance conditions, there is a slight pressure difference between the chambers. Fluid can slowly flow through the connecting holes, gradually balancing the internal pressure of all chambers. This eliminates the additional compressive stress caused by the long-term pressure difference on both sides of the partition plates, preventing the partition plates from deforming and breaking under long-term pressure. In contrast, water hammer impact is an instantaneous high-speed shearing process with extremely short pressure change duration. The fluid does not have time to flow in large quantities through the small connecting holes, thus not diluting the fluid concentration in the impact area and not weakening the impact resistance effect of the fluid's instantaneous thickening and solidification.

[0024] In one optional embodiment, the sealing cavity is provided with a sealing membrane on both the side near the outer bearing layer and the side near the inner bearing layer; The sealing cavity is provided with a sealing strip at the junction of the circumferential partition and the longitudinal partition.

[0025] Beneficial effects: A sealing membrane is completely laid on both sides of the sealing cavity, tightly adhering to both the outer and inner bearing layers. This isolates the shear-thickened fluid inside the interlayer from the external groundwater, preventing groundwater dilution and contamination of the fluid by sediment and impurities within the cavity. Sealing strips are fitted at the joints between the circumferential and longitudinal partitions to seal the assembly gaps between the rigid partitions, resolving leakage defects at these joints. The sealing membrane and sealing strips form a comprehensive closed-loop sealing system, doubly blocking fluid leakage channels from the cavity wall and partition joints, ensuring no fluid loss during long-term underwater service.

[0026] In one optional embodiment, the outer bearing layer is a reinforced concrete structure; And / or, the inner bearing layer is a reinforced concrete structure; And / or, the thickness of the thickened fluid interlayer is 10mm~20mm.

[0027] Beneficial effects: Both the outer and inner load-bearing layers are made of reinforced concrete. The concrete is easy to form and has high compressive and crack resistance. It can stably resist long-term surrounding rock pressure and internal water pressure, and is suitable for the structural load-bearing requirements of large-section, high-head water conveyance tunnels. New tunnels can be cast in one piece, and old and damaged tunnels can also be reinforced and renovated with internal lining. It has a wide range of applications.

[0028] The thickness of the thickened fluid interlayer is limited to 10mm~20mm. If the interlayer thickness is less than 10mm, the sliding buffer stroke between the two bearing layers is insufficient, and the slow deformation and temperature expansion of the surrounding rock cannot be fully released, making it easy for residual stress cracks to occur inside the lining. If the interlayer thickness is greater than 20mm, the overall rigidity of the double-layer lining structure is insufficient, and the deformation of the lining is too large under normal water conveyance conditions, posing a risk of structural instability and excessive deformation. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a water conveyance tunnel lining according to an embodiment of the present invention; Figure 2 for Figure 1 The diagram shows the structure of the thickened fluid interlayer. Figure 3 for Figure 1 Schematic diagram of the middle sealing cavity; Figure 4 for Figure 1 Schematic diagram of the structure of the sealing membrane; Figure 5 This is a schematic diagram illustrating the changes in shear rate and viscosity of the shear-thickened fluid according to an embodiment of the present invention. Figure 6 This is a comparison diagram of the stress-time curves of the lining under water hammer pressure according to an embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures: 1. Outer bearing layer; 2. Inner bearing layer; 3. Thickened fluid interlayer; 4. Separation structure; 401. Circumferential partition; 402. Longitudinal partition; 5. Sealing cavity; 6. Connecting hole; 7. Sealing membrane; 8. Sealing strip. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The following is combined with Figures 1 to 6 The following describes embodiments of the present invention.

[0034] According to an embodiment of the present invention, a water conveyance tunnel lining is provided, comprising: Outer bearing layer 1 is used to withstand external pressure on the tunnel; Inner bearing layer 2 is located inside the outer bearing layer 1 and is used to withstand the internal pressure of the tunnel. Thickened fluid interlayer 3 is disposed between the outer bearing layer 1 and the inner bearing layer 2, and the thickened fluid interlayer 3 is filled with shear thickened fluid. Shear-thickened fluids can change their viscosity according to changes in the internal or external pressure of the tunnel, so that they can solidify when the tunnel is subjected to internal or external pressure.

[0035] The core layered structure employs a double-layered bearing structure with a thickened fluid interlayer 3 sandwiched between the two layers. The outer bearing layer 1 independently bears the compression load of the tunnel surrounding rock and external pressures such as groundwater seepage pressure, while the inner bearing layer 2 independently resists the internal water pressure from the water transport medium inside the tunnel. The stress boundaries of the two bearing layers are clear, and the loads are separated. Compared with the defects of traditional single-layer integral concrete lining, which suffers from severe stress concentration due to the superposition of internal and external loads, the double-layer structure can disperse the internal and external loads, significantly improving the overall load-bearing safety redundancy of the lining. A thickened fluid interlayer 3 is specially set between the two bearing layers, and the interlayer is filled with shear-thickened fluid. This shear-thickened fluid can autonomously change its viscosity according to the relative deformation rate of the two bearing layers caused by the external pressure inside the tunnel. Once subjected to instantaneous impact loads, it can quickly solidify and lock the two layers together.

[0036] Under static and slow working conditions such as slow surrounding rock creep, slow venting and maintenance, and slow external pressure loading in a long-term stable water conveyance tunnel, the inner and outer bearing layers 1 only undergo low-speed, minute relative displacement. The shear-thickened fluid maintains a low-viscosity, flowable state, allowing for free, small-amplitude sliding between the two layers. The slow deformation of the surrounding rock, the temperature expansion and contraction stress of the concrete, and the additional stress generated by the long-term stable internal and external water pressure can all be completely buffered and released through the flexible flow of the interlayer fluid. The stress is not directly and rigidly transmitted to the concrete body, thus reducing defects such as circumferential and longitudinal penetrating cracks and surface cracking in the lining from the root cause.

[0037] When the pump station's start-stop valves rapidly open and close, generating millisecond-level water hammer impacts, causing a sudden rise and fall in pressure inside the tunnel, the inner and outer bearing layers 1 undergo high-speed relative shearing motion. The viscosity of the shear-thickened fluid in the interlayer increases dramatically and solidifies rapidly, rigidly locking the outer bearing layer 1 and inner bearing layer 2, which were originally able to slide relative to each other, into one. The overall stiffness of the lining increases several times in a short period of time, directly offsetting and weakening the instantaneous pressure peak caused by the water hammer, and preventing the impact stress concentration from penetrating the concrete lining.

[0038] The entire structure can adapt to various working conditions, eliminating the need for uniformly thickening the lining reinforcement and increasing the concrete thickness according to extreme peak water hammer loads. This significantly reduces the amount of reinforced concrete used, effectively lowering the overall cost of the tunnel project. Furthermore, the stiffness is passively adjusted entirely by the fluid's own material properties, eliminating the need for external auxiliary equipment such as sensors, electrical control systems, hydraulic pipelines, and pressure regulating valves. This avoids issues like pipeline blockages, electrical malfunctions, and regular valve maintenance. It is suitable for the entire layout of water conveyance tunnels spanning tens of kilometers, simplifying construction procedures and significantly reducing subsequent maintenance workload.

[0039] Specifically, the viscosity change of shear-thickened fluid is completely reversible. After the impact load disappears, the fluid can quickly return to a low-viscosity flow state and can withstand more than a million repeated shear cycles without failure.

[0040] Specifically, the shear-thickened fluid is a suspension of nanoparticles.

[0041] By defining the shear-thickened fluid as a nanoparticle suspension, the nanoscale solid particles can be uniformly dispersed and suspended in the liquid medium, exhibiting excellent fluidity. This allows the fluid to completely fill the narrow spaces within the thickened fluid interlayer, preventing the problem of localized areas lacking effective fluid filling due to particle deposition. Simultaneously, the large specific surface area of ​​the nanoparticles enables them to rapidly form a contact network under shear stress, achieving a viscosity change response speed in milliseconds. Compared to conventional large-particle thickened fluids, this suspension system is more sensitive to instantaneous impacts, precisely matching the protection requirements against water hammer. Under static low-speed deformation conditions, the fluid flows uniformly, maintaining consistent buffering deformation capacity throughout the interlayer, eliminating any weak points in localized buffering failure.

[0042] like Figure 5 As shown, shear-thickened fluids at shear rates less than 10 s⁻¹ - At ¹, the fluid viscosity of the shear-thickened fluid is less than 5 Pa·s; Shear-thickened fluids at shear rates greater than 10 s⁻¹ - ¹When the shear-thickened fluid viscosity is greater than 500 Pa·s.

[0043] Under low-speed static deformation conditions, the fluid flow resistance is minimal, and the sliding between the inner and outer load-bearing layers is smooth. Minor creep of the surrounding rock, temperature expansion and contraction of the concrete, and slow water pressure deformation can all be fully absorbed by the interlayer, preventing residual additional stress within the lining. As the shear rate increases, the viscosity can increase by hundreds of times. Upon high-speed shear impact, the fluid loses its fluidity, forming a solid load-bearing medium that firmly restricts the relative displacement of the inner and outer load-bearing layers, significantly improving the overall impact and deformation resistance of the lining. The two sets of viscosity parameters create a significant performance difference, clearly defining the two independent working states of static buffering and impact reinforcement. The boundary between working conditions is clear, preventing intermediate transitions of insufficient buffering or reinforcement failure, ensuring stable and reliable operation of the lining in both working modes.

[0044] Specifically, the shear-thickened fluid includes a suspension of mixed nanoparticles of nano-silica and polyethylene glycol PEG-400.

[0045] Nano-silica is selected as the solid phase particles, which have high hardness and strong mechanical stability, and will not show any particle breakage or performance degradation after tens of millions of shear thickening cycles. Polyethylene glycol (PEG-400) is used as the liquid phase carrier, which is water-resistant, resistant to high and low temperatures, and does not easily volatilize. It will not be diluted or lost even after long-term immersion in the humid water environment of the tunnel, making it perfectly suitable for the permanent underwater service environment of the tunnel. The suspension formed by the two compounds has excellent compatibility and will not show solid-liquid separation even after long-term static standing at room temperature. Compared with oil-based organic solvent-based thickening fluids, the water-based PEG medium is non-corrosive and will not erode the concrete bearing layers and rubber sealing components on both sides. Long-term use will not damage the main lining structure and sealing system.

[0046] Specifically, shear-thickened fluids also include ammonium polyacrylate dispersants, fumed silica anti-settling agents, and antioxidants.

[0047] Ammonium polyacrylate dispersant can encapsulate nano-silica particles, eliminating electrostatic agglomeration between particles and ensuring long-term uniform dispersion of nanoparticles in the PEG liquid phase. Fumed silica, acting as an anti-settling agent, enhances the suspension and support capacity of the liquid medium. Even during long-term shutdown and stagnant operation of the tunnel, solid particles will not settle and accumulate at the bottom of the interlayer, maintaining consistent fluid performance throughout the entire interlayer. Antioxidants can delay the oxidative aging of the polyethylene glycol liquid phase, preventing deterioration and failure of the medium under long-term high-temperature underwater conditions, significantly extending the overall service life of the shear-thickened fluid, and reducing maintenance work required for subsequent fluid replenishment and replacement.

[0048] Specifically, the raw material ratio parameters for shear-thickened fluid are as follows: the solid phase particles are selected as nano-silica with a particle size of 20nm and an overall solid content of 45wt%; the liquid phase medium is polyethylene glycol PEG-400; the additives include 0.5wt% ammonium polyacrylate dispersant, 0.3wt% fumed silica anti-settling agent, and 0.2wt% antioxidant.

[0049] Performance tests were conducted on the shear-thickened fluid at this formulation, and the results are as follows: shear rate was 10 s⁻¹. - The fluid viscosity was 3.2 Pa at ¹. s; shear rate is 200s - ¹The fluid viscosity is 820 Pa. The viscosity increased by approximately 256 times; the overall fluid response time was less than 5 ms.

[0050] This precise formulation ensures that the nano-silica particles are stably dispersed within the liquid medium, and various additives work synergistically to prevent particle agglomeration and sedimentation, as well as aging and deterioration of the liquid medium. Simultaneously, the fluid exhibits a significant viscosity difference under high and low shear conditions, resulting in extremely fast response times during condition switching. It can rapidly thicken and solidify under the instantaneous high-speed shearing action generated by water hammer impact, while maintaining low-viscosity flow characteristics during the static, slow deformation stage. The two working states are clearly distinguishable, ensuring stable adaptation to various load conditions during the long-term service of water conveyance tunnels.

[0051] like Figure 6 As shown, during the stable water conveyance stage (t < 0.5s), the stress of both the traditional lining and the STF sandwich lining structures remained stable at the design value of 8MPa, and both linings could meet the bearing requirements of conventional water conveyance loads. When the water hammer impact load was applied at t = 0.5s, the stress on both curves rose rapidly and synchronously, but the peak stress and attenuation patterns showed significant differences. The peak stress of the traditional lining could reach 28MPa, far exceeding the design stress of 8MPa, significantly exceeding the long-term safe bearing limit of concrete, with a longer sustained high stress range. The subsequent secondary stress peaks reached 17MPa and 14MPa respectively, forming multiple high-intensity cyclic impacts. The maximum peak stress of the STF sandwich lining of this invention was only 18MPa, with a peak stress reduction of more than 35% compared to the traditional lining. The impact stress fell back faster, and there were no significant excessive secondary stress fluctuations. In the later stages of the impact, the stress could quickly fall back to the steady-state design stress of 8MPa.

[0052] The test curve confirms the adaptive protection effect of the shear-thickened fluid in the interlayer of the present invention. Under the instantaneous impact of water hammer, the fluid rapidly thickens and solidifies, effectively dispersing and reducing the peak stress transmitted to the concrete lining, and significantly reducing the risk of lining cracking and damage. After the impact ends, the fluid returns to a low-viscosity flow state, and the lining stress steadily returns to the normal design value, taking into account both static water conveyance stability and instantaneous impact protection capability.

[0053] like Figure 1 As shown, it also includes a partition structure 4, which is disposed within the thickened fluid interlayer 3 and is used to partition the shear thickened fluid into sections. Separation structure 4 includes: Circumferential baffle 401 is arranged in the circumferential direction along the thickened fluid interlayer 3; Longitudinal partitions 402 are arranged at intervals along the axial direction of the thickened fluid interlayer 3.

[0054] By circumferential baffles 401 arranged around the tunnel circumference and longitudinal baffles 402 arranged at intervals along the tunnel length axis, the thickened fluid interlayer 3 of the entire long tunnel is divided into multiple independent sections through their interlocking arrangement. Without the separation structure 4, the entire interlayer would be interconnected, and due to the tunnel's slope and long-term unidirectional stress, the fluid would easily shift and accumulate to one end, causing local fluid shortages and loss of buffering and protective capabilities. This separation structure 4 restricts the fluid movement range, with a fixed fluid volume within each section, resulting in uniform fluid distribution throughout the tunnel. When water hammer occurs at any location, the fluid in the corresponding section can independently undergo shearing and thickening, without weakening the local impact resistance due to large-scale fluid flow and dispersion.

[0055] As an alternative implementation method, the partition structure 4 can be made of rigid high-density plastic sheet instead of steel plate, which is suitable for water conveyance tunnels with low water head and no strong groundwater corrosion.

[0056] like Figure 3 As shown, the circumferential partition 401 and the longitudinal partition 402 together form several sealed cavities 5, and the shear-thickened fluid is contained inside the sealed cavities 5.

[0057] The partitions enclose and form independent, sealed cavities 5, which individually enclose the shear-thickened fluid within their respective cavities. The fluid is physically isolated and will not move freely within the interlayer. Each independent cavity can independently bear the internal and external pressures of its corresponding area. The load differences between different tunnel sections will not interfere with each other, preventing local high-pressure fluid from being squeezed into low-pressure areas and causing overall stress imbalance. At the same time, the independent sealing of the cavities means that if a minor leak occurs in a single cavity, it will only affect the fluid in that section and will not cause the entire interlayer fluid to be lost. The scope of the fault is controllable, and subsequent repair and injection of fluid only requires treatment of the corresponding cavity, significantly reducing the workload of maintenance.

[0058] Specifically, the sealing cavity 5 is provided with connecting holes 6 at the positions of the circumferential partition 401 and the longitudinal partition 402, which are used to achieve pressure equalization of the shear-thickened fluid.

[0059] Adjacent sealed cavities 5 are interconnected via partition connecting holes 6. Under long-term static water supply and venting maintenance conditions, a slight pressure difference exists between the cavities. Fluid can slowly flow through the connecting holes 6, gradually balancing the internal pressure of all cavities. This eliminates the additional compressive stress caused by the long-term pressure difference on both sides of the partition, preventing the partition from deforming and breaking under long-term pressure. Water hammer impact is an instantaneous high-speed shearing process with an extremely short duration of pressure change. The fluid does not have time to flow in large quantities through the small connecting holes 6, thus not diluting the fluid concentration in the impact area and not weakening the impact resistance effect of the fluid's instantaneous thickening and solidification.

[0060] Specifically, the circumferential baffle 401 and the longitudinal baffle 402 are provided with throttling and connecting holes 6 with a diameter of 10 mm. The fluid pressure equalization time between adjacent chambers is about 30 minutes. The slow pressure equalization will not interfere with the shear thickening response of the instantaneous water hammer.

[0061] like Figure 2 and Figure 4 As shown, the sealing cavity 5 is provided with a sealing membrane 7 on both the side near the outer bearing layer 1 and the side near the inner bearing layer 2; The sealing cavity 5 is provided with a sealing strip 8 at the junction of the circumferential partition 401 and the longitudinal partition 402.

[0062] A sealing membrane 7 is completely laid on both sides of the sealed cavity 5, closely adhering to the outer bearing layer 1 and the inner bearing layer 2. This isolates the shear-thickened fluid inside the interlayer from the external groundwater, preventing groundwater dilution and contamination of the fluid by sediment and impurities within the cavity. A sealing strip 8 is fitted at the joint between the circumferential partition 401 and the longitudinal partition 402 to seal the assembly gaps between the rigid partitions, thus resolving leakage defects at these joints. The sealing membrane 7 and the sealing strip 8 form a comprehensive closed-loop sealing system, doubly blocking fluid leakage channels from the cavity wall and partition joint gaps, ensuring no fluid loss during long-term underwater service.

[0063] Specifically, the sealing membrane 7 and sealing strip 8 can be made of rubber, which is suitable for the entire temperature range of the tunnel environment.

[0064] Specifically, the outer load-bearing layer 1 is a reinforced concrete structure; Specifically, the inner load-bearing layer 2 is a reinforced concrete structure; Specifically, the thickness of the thickened fluid interlayer 3 is 10mm~20mm.

[0065] Both the outer and inner bearing layers are made of reinforced concrete. The concrete is easy to form and has high compressive and crack resistance. It can stably resist long-term surrounding rock pressure and internal water pressure, and is suitable for the structural bearing requirements of large-section, high-head water conveyance tunnels. New tunnels can be cast in one piece, and old and damaged tunnels can also be reinforced and renovated with internal lining. It has a wide range of applications.

[0066] The thickness of the thickened fluid interlayer 3 is limited to 10mm~20mm. If the interlayer thickness is less than 10mm, the sliding buffer stroke between the two bearing layers is insufficient, and the slow deformation and temperature expansion of the surrounding rock cannot be fully released, making it easy for residual stress cracks to occur inside the lining. If the interlayer thickness is greater than 20mm, the overall structural rigidity of the double-layer lining is insufficient, and the lining deformation is too large under normal water conveyance conditions, posing a risk of structural instability and excessive deformation.

[0067] Specifically, the outer bearing layer 1 is made of C40 grade reinforced concrete and has a solid thickness of 250mm; the inner bearing layer 2 is made of C50 grade reinforced concrete and has a solid thickness of 400mm; the thickened fluid interlayer 3 has a uniform thickness of 15mm.

[0068] In this embodiment, a partition structure 4 and a sealing structure are provided. The partition structure 4 is made of a 5mm thick steel plate to form a rigid partition. The circumferential partition 401 is arranged along the tunnel axis with a spacing of 5m between adjacent partitions. The longitudinal partition 402 is arranged along the circumference of the tunnel, dividing the interlayer into independent fan-shaped chambers. The sealing structure has a 5mm thick rubber sealing membrane 7 laid on the inner and outer sides of the interlayer. All splicing edges of the sealing membrane 7 are fitted with rubber sealing strips 8 to achieve overall sealing.

[0069] The outer bearing layer 1 uses lower strength C40 concrete with a thickness of 250mm to stably bear the load of surrounding rock and external groundwater, controlling the civil engineering cost while meeting the external pressure requirements; the inner bearing layer 2 is in direct contact with the water body conveyed in the tunnel and bears the high-frequency internal water pressure. It uses higher strength C50 concrete and is thickened to 400mm to improve the inner layer's impermeability and crack resistance, and avoid surface damage and leakage caused by long-term internal pressure.

[0070] The interlayer is set at the middle value of 15mm, which provides sufficient sliding buffer space to release static deformation stress without significantly weakening the overall rigidity of the double-layer lining, thus balancing the buffering effect and structural stability.

[0071] The steel plate partitions are rigid enough, and the 5mm thickness can withstand long-term compression of fluid in the cavity without deformation. The 5m circumferential spacing combined with the equally divided longitudinal partitions ensures that the volume of each fan-shaped cavity is uniform, the fluid distribution in the entire interlayer is balanced, and any impact at any location can be independently sheared and thickened for protection.

[0072] The double-layer 5mm rubber sealing membrane 7, together with the edge sealing strip 8, forms a complete sealing barrier, isolating the internal and external water bodies from the shear-thickened fluid inside the interlayer, effectively preventing fluid dilution and loss, and impurities from invading and contaminating the fluid, ensuring that the fluid in the interlayer maintains stable rheological properties over a long period of time.

[0073] When this structure is installed in a water conveyance tunnel with a total length of 35km, a diameter of 4.5m, a maximum internal water pressure of 8.5MPa, and a risk of water hammer, the tunnel excavation and initial support of the surrounding rock are completed first, and the loose surrounding rock of the tunnel is reinforced.

[0074] Subsequently, reinforcing bars were tied and a 250mm thick C40 outer bearing layer 1 was poured. Metal tie rods with 1m x 1m spacing were pre-embedded and cured. A 5mm rubber outer sealing membrane 7 was hot-melt welded onto the inner wall of the outer layer. Longitudinal steel plate partitions 402 were installed every 5m along the tunnel axis, and circumferential partitions 401 were evenly distributed around the circumference to form eight fan-shaped sealing cavities 5. Sealant was applied to the junction of the partitions and the sealing membrane 7. Then, an inner 5mm rubber sealing membrane 7 was laid, and sealing strips 8 were added to the joints of the partitions for sealing. Afterwards, reinforcing bars were tied and a 400mm thick C50 inner bearing layer 2 was poured. After curing, fluid injection holes and vent holes were reserved. Finally, the prepared shear-thickened fluid was injected into each cavity through the reserved holes. After the air inside the cavity was purged, the holes were sealed, completing the overall construction and installation.

[0075] After the tunnel is filled with water and enters long-term water conveyance operation, the stress changes in the lining can be continuously monitored. Under static load conditions such as daily stable water conveyance and venting maintenance, the interlayer fluid maintains a low-viscosity flow state to release deformation stress. When the pump station starts or stops, or when valve misoperation causes water hammer impact, the shear-thickened fluid instantly thickens and solidifies, increasing the overall stiffness of the lining and buffering the impact peak. After the impact disappears, the fluid automatically restores its flow characteristics and continues to serve. If the fluid performance deteriorates after long-term use, it can be replenished or replaced simply through the reserved injection holes without dismantling the main lining structure, making operation and maintenance simple.

[0076] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A lining for a water conveyance tunnel, characterized in that, include: The outer bearing layer (1) is used to withstand the external pressure of the tunnel; Inner bearing layer (2), which is disposed inside the outer bearing layer (1) and is used to withstand the internal pressure of the tunnel; Thickened fluid interlayer (3), the thickened fluid interlayer (3) is disposed between the outer bearing layer (1) and the inner bearing layer (2), and the thickened fluid interlayer (3) is filled with shear thickened fluid; The shear-thickened fluid can change its viscosity when shear force is generated by internal or external pressure in the tunnel, so that the shear-thickened fluid can solidify when subjected to shear force.

2. The water conveyance tunnel lining according to claim 1, characterized in that, The shear-thickened fluid is a suspension of nanoparticles.

3. The water conveyance tunnel lining according to claim 2, characterized in that, The shear-thickened fluid has a shear rate of less than 10 s. - ¹When the shear-thickened fluid viscosity is less than 5 Pa·s; The shear-thickened fluid has a shear rate greater than 10s. - ¹When the shear-thickened fluid has a viscosity greater than 500 Pa·s.

4. The water conveyance tunnel lining according to claim 2, characterized in that, The shear-thickened fluid comprises a suspension of mixed nanoparticles of nano-silica and polyethylene glycol PEG-400.

5. The water conveyance tunnel lining according to claim 4, characterized in that, The shear-thickened fluid also includes ammonium polyacrylate dispersant, fumed silica anti-settling agent, and antioxidant.

6. The water conveyance tunnel lining according to claim 1, characterized in that, It also includes a partition structure (4), which is disposed within the thickened fluid interlayer (3) for dividing the shear thickened fluid into partitions; The partition structure (4) includes: Circumferential partition (401) is arranged along the circumferential direction of the thickened fluid interlayer (3); Longitudinal partitions (402) are arranged at intervals along the axial direction of the thickened fluid interlayer (3).

7. The water conveyance tunnel lining according to claim 6, characterized in that, The circumferential partition (401) and the longitudinal partition (402) together form a plurality of sealed cavities (5), and the shear-thickened fluid is contained inside the sealed cavities (5).

8. The water conveyance tunnel lining according to claim 7, characterized in that, The sealed cavity (5) has a connecting hole (6) at the positions of the circumferential partition (401) and the longitudinal partition (402) to achieve pressure equalization of the shear-thickened fluid.

9. The water conveyance tunnel lining according to claim 7, characterized in that, The sealing cavity (5) is provided with a sealing membrane (7) on the side near the outer bearing layer (1) and the side near the inner bearing layer (2). The sealing cavity (5) is provided with a sealing strip (8) at the enclosing position of the circumferential partition (401) and the longitudinal partition (402).

10. The water conveyance tunnel lining according to any one of claims 1-9, characterized in that, The outer bearing layer (1) is a reinforced concrete structure; And / or, the inner bearing layer (2) is a reinforced concrete structure; And / or, the thickness of the thickened fluid interlayer (3) is 10mm~20mm.

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