Gravity dam crack control construction device and process based on constructing strain gradient

Abstract

The present invention proposes a construction device and process for controlling cracks in a gravity dam based on the construction of a strain gradient, belonging to the field of gravity dam technology. The construction device includes an outer tube assembly and an inner tube assembly used in conjunction with the outer tube assembly; the process includes S1. Construction preparation, S2. Foundation treatment, S3. Installation of formwork reinforcement, S4. Installation of the outer tube assembly, S5. Concrete pouring, S6. Hole construction, S7. Positioning and installation of the inner tube assembly, S8. Filling the outer layer with stress-absorbing material, S9. Pulling out the inner tube assembly, and S10. Filling the inner layer with stress-absorbing material creates a concentric strain gradient structure. This invention breaks away from the traditional "strong constraint" crack resistance approach and turns to an active crack resistance mode of "stress absorption + gradient buffering." The gradient conduction mechanism allows the two layers of material to share the load more evenly, improving overall energy efficiency, achieving a more significant crack resistance effect, and enhancing structural durability. It is particularly suitable for the construction of high dams and gravity dams under complex geological conditions, and has significant engineering application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of gravity dams, and in particular relates to a construction device and process for controlling cracks in a gravity dam based on constructing a strain gradient. Background Art

[0002] Gravity dams, as key facilities in water conservancy projects, play an important role in regulating water resources, preventing floods and reducing disasters, and ensuring water supply for agricultural production and residents. Dam cracks have always been a key and difficult research topic for scholars at home and abroad. Existing technologies mainly focus on crack control from three perspectives:

[0003] From the material perspective: using medium- and low-heat cement, optimizing the concrete mix ratio, reducing the amount of cementitious materials, adjusting the concrete aggregate gradation, and applying shrinkage compensation methods can reduce the concrete temperature rise and the risk of concrete cracking from the perspective of concrete composition materials;

[0004] From the perspective of construction technology: concrete is constructed in separate compartments and layers, cooling circulating water pipes are buried in the concrete to reduce the mixing water temperature, pre-cool the aggregate, reduce the heat in the concrete, reduce the temperature difference between the inside and outside of the concrete, improve the temperature field distribution, and reduce temperature stress;

[0005] From the perspective of concrete maintenance: use methods such as intelligent spraying and covering insulation to reduce the temperature difference between the inside and outside of the concrete.

[0006] Research and practice have shown that these technical measures have, to a certain extent, reduced the thermal and shrinkage stresses in dam concrete, lowering the risk of dam cracking. However, internal stresses within the dam structure are the root cause of concrete cracking. Therefore, eliminating these internal stresses is crucial for addressing cracking during construction and operation of concrete gravity dams. Existing research methods, whether targeting concrete thermal stress or concrete shrinkage stress, have struggled to fundamentally eliminate internal stresses within the dam and suffer from insufficient internal stress regulation.

[0007] Therefore, how to optimize the internal stress distribution of the dam, reduce stress concentration, and develop a gradient-changing stress absorption construction device and method that can be integrated into the dam body, has strong interface bonding ability, and is feasible for construction, has become a key breakthrough direction for solving the problem of cracks in gravity dams. Summary of the Invention

[0008] Based on the problems existing in the background technology, the present invention proposes a construction device and process for controlling cracks in a gravity dam based on constructing a strain gradient.

[0009] In a first aspect, the present technical solution proposes a construction device for controlling cracks in a gravity dam based on constructing a strain gradient, comprising an outer tube assembly and an inner tube assembly used in conjunction with the outer tube assembly, wherein the inner tube assembly comprises a first tube body, the outer wall of which is wrapped with a first spring hose in a spiral pattern; the bottom end of the first tube body is open;

[0010] The outer tube assembly includes a second tube body, the bottom end of the second tube body has a closed sealing plate and the top end is open; the center of the sealing plate has a positioning hole recessed toward the top end of the second tube body, and a positioning boss is formed at the positioning hole after concrete is poured, and the bottom end of the first tube body can be positioned and plugged into the positioning boss; the second tube body is provided with at least one group of hole arrays on the tube wall, and the hole array includes a number of spaced through holes arranged along the height direction of the second tube body; a vertical strip is provided in the internal cavity of the second tube body, and the strip is fixedly connected to the inside of the second tube body; a number of column heads that can be adapted and plugged into the through holes are provided on the strip head, and the column heads are slidably connected to the strip heads; a compression spring is provided on the column head, one end of the compression spring is connected to one end of the column head, and the other end is connected to the strip head; when external force squeezes one end of the column head, the column head can move, and the other end of the column head extends outward through the through hole.

[0011] Preferably, the outer tube assembly further comprises a second airbag, a mounting space is formed between the plurality of strips, and the second airbag can be placed in the mounting space; the second airbag is provided with an inflatable / deflated valve.

[0012] Preferably, a sealing ring is provided on the hole wall of the through hole, and the column head can be connected to the sealing ring in a sealing and sliding manner.

[0013] Preferably, the column head is cylindrical, conical or polygonal.

[0014] Preferably, one end of the column head is connected to an end plate, and one end of the compression spring is connected to the end plate.

[0015] Preferably, a second spring hose is wound around the outer wall of the second tube body, and the second spring hose does not interfere with the column head.

[0016] Preferably, the first spring hose and / or the second spring hose are filled with gas or liquid medium.

[0017] Secondly, this technical solution proposes a construction process for controlling cracks in a gravity dam based on the construction of a strain gradient, and adopts a construction device for controlling cracks in a gravity dam based on the construction of a strain gradient, comprising the following steps:

[0018] S1. Construction preparation: diversion, site leveling, and material preparation;

[0019] S2. Foundation treatment: dam foundation excavation, bedrock treatment and grouting;

[0020] S3. Install formwork reinforcement: erect formwork and tie reinforcement;

[0021] S4. Install the outer tube assembly: Position and install the outer tube assembly in the designed position;

[0022] S5. Concrete pouring: pouring in blocks and layers, temperature-controlled vibration, and curing;

[0023] S6. Cavity Construction: After the concrete has initially set, remove the outer tube assembly to form a cavity with a concave-convex interface. This interface is referred to as the outer occlusal boundary.

[0024] S7. After checking that the bore meets the design requirements, coaxially position and install the inner tube assembly within the bore.

[0025] S8. Filling an outer layer of stress-absorbing material: Filling an outer layer of stress-absorbing material in the area between the cavity and the inner tube assembly, the outer layer of stress-absorbing material being integrally connected to the inner wall of the cavity, forming a mosaic structure at the boundary;

[0026] S9. After the outer layer stress-absorbing material has initially solidified, the inner tube assembly is pulled out of the tube. A central hole with a spiral groove interface is formed upon removal. This interface is recorded as the inner layer occlusal boundary.

[0027] S10. Fill the central hole with an inner layer of stress absorbing material, and after filling, form a bite-type interface between the inner layer of stress absorbing material and the outer layer of stress absorbing material; at the same time, construct a concentric circle strain gradient structure in the cavity; multiple cavities form a distributed stress absorbing hole group with strain gradient.

[0028] Preferably, the method for constructing the S6 mesopore is:

[0029] During construction, an uninflated second airbag is placed in the installation space of the strip board, and then the second airbag is inflated. The second airbag is inflated and bulges, squeezing one end of the column head. The compression spring is compressed, and the other end of the column head extends out through the through hole. After pouring concrete, the column head exposed outside the second tube body is buried in the concrete.

[0030] After the concrete has initially set, the second airbag is deflated and the column head moves backward into the second tube body under the elastic force of the compression spring. After the column head withdraws, a recessed portion is formed in the concrete. Subsequently, the second airbag and the second tube body are pulled out to form a cavity with a hole array.

[0031] Preferably, the specific installation method of the inner tube assembly in S7 is:

[0032] After the second tube body is demoulded, a positioning boss is formed at the bottom of the cavity. The bottom end of the first tube body is inserted into the cavity and fixed with the positioning boss, forcing the centering limit at the bottom of the cavity. Subsequently, the top of the first tube body is fixed to form a top limit to ensure the coaxiality of the first tube body and the cavity.

[0033] The specific method for removing the inner tube assembly in S9 is as follows:

[0034] The top of the first spring hose is separated from the first tube body, and the first tube body is lifted up. The first tube body can slide relative to the first spring hose, and the first tube body can also slide relative to the first spring hose. Since the bottom end of the first spring hose is fixedly connected to the bottom end of the first tube body, as the first tube body moves upward, the first tube body simultaneously pulls the first spring hose to move, thereby pulling the first spring hose out of the concrete.

[0035] As the first tube body continuously moves upward, the first spring hose is continuously separated from the concrete, and a spiral groove is formed after the separation; when the first tube body is completely pulled out, a central hole with a spiral groove is formed.

[0036] The above technical solution has the following advantages:

[0037] 1. This invention breaks through the traditional "strong constraint" anti-cracking idea and turns to the active anti-cracking mode of "stress absorption + gradient buffering". It is particularly suitable for the construction of high dams and gravity dams under complex geological conditions, and has significant engineering application value.

[0038] 2. The construction device designed in the present invention forms an outer bite boundary and an inner bite boundary at the interface after the tube is pulled out, so that bite-type interfaces are formed between the outer stress-absorbing material and the concrete, and between the outer stress-absorbing material and the inner stress-absorbing material, respectively. This increases the interface roughness and contact area, enhances the overall synergistic effect, and significantly improves the shear strength through mechanical bite. Compared with a straight interface, it can effectively inhibit interlayer slip cracking and effectively improve the interface mechanical properties.

[0039] 3. The present invention adopts a staged extubation and filling process to ensure that the stress absorbing material is clearly layered and has high density, avoids mixing or uneven filling, and ensures that the strain gradient is accurately formed.

[0040] 4. This process creates a strain-gradient active stress absorption system. The two layers of material form a gradient, gradually absorbing strain. This gradient distribution of material properties avoids the concentrated cracking caused by sudden stress changes in traditional structures, allowing strain to be released gradually along the radial direction, reducing the probability of crack initiation. The gradient conduction mechanism of the strain-gradient structure allows the two layers of material to share the load more evenly, improving overall energy efficiency. Through material deformation and interfacial energy dissipation, stress levels are fundamentally reduced, crack resistance is more significant, and the structure can adapt to dynamic loads and environmental changes, enhancing its durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the specific implementation or the description of the prior art.

[0042] Figure 1 3 is a cross-sectional view of the structure of the outer tube assembly in Example 1.

[0043] Figure 2 yes Figure 1 Top view of the inner and outer tube components before being cut open.

[0044] Figure 3 This is an enlarged schematic diagram of the structure of area A.

[0045] Figure 4 This is a schematic diagram of the structure of the inner tube assembly Figure 1 .

[0046] Figure 5 It is a structural diagram of the first spring hose.

[0047] Figure 6 It is a structural schematic diagram of the strain gradient structure set in the gravity dam.

[0048] Figure 7 It is an enlarged cross-sectional view of a single cavity before it is filled with the outer layer of stress absorbing material.

[0049] Figure 8 It is a construction flow chart of the strain gradient structure during construction.

[0050] Description of reference numerals:

[0051] 1. Dam foundation; 2. Dam body; 3. Strain gradient structure; 31. Outer layer stress absorbing material; 32. Inner layer stress absorbing material; 4. Cavity; 41. Positioning boss; 5. Recessed portion; 6. First tube body; 7. First spring hose; 8. Closing plate; 81. Positioning hole; 9. Center hole; 10. Second tube body; 11. Strip plate; 12. Through hole; 13. Column head; 14. Compression spring; 15. End plate; 16. Second airbag; 17. Sealing ring. DETAILED DESCRIPTION

[0052] The following embodiments of the technical solution of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only examples and are not intended to limit the scope of protection of the present invention.

[0053] Example 1:

[0054] like Figure 1 - Figure 8 As shown, this embodiment proposes a gravity dam crack control construction device based on constructing a strain gradient, which includes an outer tube assembly and an inner tube assembly used in conjunction with the outer tube assembly. The inner tube assembly includes a first tube body 6, and the outer wall of the first tube body 6 is wrapped with a first spring hose 7 in a spiral pattern; the bottom end of the first tube body 6 is open.

[0055] The outer tube assembly includes a second tube body 10, the bottom end of the second tube body 10 has a closed sealing plate 8, and the top end is open; the center of the sealing plate 8 has a positioning hole 81 recessed toward the top end of the second tube body 10, the axis of the positioning hole 81 coincides with the axis of the second tube body 10, and a positioning boss 41 can be formed at the positioning hole 81 after concrete pouring, and the bottom end of the first tube body 6 can be adapted to be positioned and plugged with the positioning boss 41; the second tube body 10 is provided with at least one group of hole arrays on the tube wall, and the hole array includes holes arranged along the height direction of the second tube body 10. A plurality of spaced through holes 12 are provided; a vertical strip 11 is provided in the internal cavity of the second tube body 10, and the strip 11 is fixedly connected to the inside of the second tube body 10; a plurality of column heads 13 that can be adapted to be plugged into the through holes 12 are provided on the strip 11, and the column heads 13 are slidably connected to the strip 11; a compression spring 14 is sleeved on the column head 13, one end of the compression spring 14 is connected to one end of the column head 13, and the other end is connected to the strip 11; when an external force squeezes one end of the column head 13, the column head 13 can move, and the other end of the column head 13 extends outward through the through hole 12.

[0056] In this embodiment, taking into account actual engineering conditions and for ease of operation, an airbag is employed to squeeze the stud 13. To this end, the outer tube assembly also includes a second airbag 16, which fits within a mounting space defined between the multiple slats 11. This second airbag 16 is equipped with an inflation / deflation valve. Initially, the stud 13 is concealed within the second tube 10. During construction, the inflated second airbag 16 squeezes the stud 13, extending it.

[0057] In some embodiments, in order to prevent the slurry from entering the second tube body 10, a sealing ring 17 is provided on the wall of the through hole 12, and the column head 13 can be sealed and slidably connected to the sealing ring 17, which can effectively achieve the slurry barrier. When the gravity dam concrete is poured and vibrated, the traditional non-sealed structure easily causes cement slurry to penetrate into the second tube body 10 through the gap between the through hole 12 and the column head 13, causing the column head 13 to become stuck and the compression spring 14 to rust and fail. The sealing ring 17 can be made of silicone rubber or fluororubber, which can completely block the concrete slurry from penetrating the channel, ensuring that the telescopic mechanism of the column head 13 is always in a clean environment and the hole-forming qualification rate is high.

[0058] In some embodiments, the inner side of the sealing ring 17 is mirror polished and lubricated with a graphite coating to effectively reduce the sliding friction of the column head 13. Even under the slight viscosity of the concrete before initial setting, rapid retraction can still be achieved through the elastic force of the compression spring 14, avoiding the risk of pipe jamming after the concrete hardens.

[0059] In this embodiment, the column head 13 has various styles, and the column head 13 is cylindrical, conical, or polygonal. In this embodiment, the column head 13 can be preferably cylindrical or conical to facilitate demoulding.

[0060] In order to facilitate the squeezing of the column head 13, one end of the column head 13 is connected to an end plate 15, and one end of the compression spring 14 is connected to the end plate 15. The design of the end plate 15 can increase the contact area and prevent the column head 13 from exerting excessive pressure on the second air bag 16 during squeezing.

[0061] The specific method of using the second airbag 16 is as follows:

[0062] During use, the uninflated second airbag 16 is placed in the installation space surrounded by the strips 11, and then the second airbag 16 is inflated. The second airbag 16 is inflated and bulged, squeezing the end plate 15. The end plate 15 compresses the compression spring 14, and the column head 13 extends out through the through hole 12. After pouring concrete, the column head 13 exposed outside the second tube body 10 is buried in the concrete; after the concrete is initially solidified, the second airbag 16 is deflated, and the second airbag 16 becomes deflated. The column head 13 moves backward into the second tube body 10 under the elastic force of the compression spring 14; after the column head 13 withdraws, a recessed portion 5 is formed in the concrete. Subsequently, the second airbag 16, the second tube body 10, etc. are pulled out to form a cavity 4 with a recessed portion 5.

[0063] The design of the second airbag 16 driving the column head 13 to expand and contract and the compression spring 14 to return to its original position realizes the formation of the regular hole-shaped recessed portion 5 in the concrete structure. The technical advantages include:

[0064] First, the structure:

[0065] 1) Hidden stud 13 design avoids interference with concrete pouring: Initially, stud 13 is concealed within second tube 10, creating a smooth surface during concrete pouring. This prevents premature contact with concrete, which could cause stuttering or deformation, ensuring dense concrete filling. After the second airbag 16 is inflated, stud 13 synchronously and stably extends through through-hole 12, forming a regular raised structure. After the concrete initially sets, stud 13 retracts, leaving a precisely defined recess 5 with a consistent diameter and depth.

[0066] 2) The hole array can be arranged in multiple groups (e.g., 2-4 groups) along the circumference, and the column heads 13 are spaced apart along the height direction. By adjusting the number of hole array groups, the spacing between the column heads 13, and the extension length, linearly arranged holes, annular hole groups, and customized hole shapes (e.g., honeycomb, tooth-shaped) can be formed to meet the functional opening requirements of different gravity dams.

[0067] 3) After the second airbag 16 is inflated, it can evenly squeeze all the studs 13 through air pressure, so that multiple studs 13 can be extended synchronously without manual adjustment one by one. This greatly shortens the assembly and positioning time of the hole-making device, making it particularly suitable for large-area, multi-hole drilling scenarios.

[0068] 4) After the concrete initially sets, the second airbag 16 deflates and the column head 13 quickly retracts into the tube body under the elastic force of the compression spring 14. This prevents the column head 13 from being retained in the concrete and forming a "barb". This reduces the friction resistance and adhesion during tube extraction, significantly improving demoulding efficiency and avoiding concrete damage or hole wall cracking caused by forced tube extraction.

[0069] 5) The column head 13 is slidably connected to the strip 11 and restrained by a compression spring 14. During inflation, the second airbag 16 provides constant squeezing pressure, ensuring that the column head 13 extends to a consistent length. During retraction, the spring tension is stable, preventing the column head 13 from getting stuck or rebounding out of position, thereby ensuring accurate hole dimensions. The strip 11, column head 13, and second airbag 16 components are independently removable and replaceable. The second tube 10 is made of a wear-resistant material (such as PVC, metal, high-strength HDPE, or a steel-plastic composite tube), and the second airbag 16 is made of anti-aging rubber. The entire device is reusable multiple times, reducing construction costs.

[0070] Second, the process:

[0071] 1. It can be adapted to the scenario of cast-in-place concrete in gravity dams. The vibration frequency of gravity dam vibration operation is high. The device is double-limited by the compression spring 14 + second airbag 16. After inflation, the column head 13 is extended and locked. The compression spring 14 provides rigid support to resist the displacement caused by the vibration force; after deflation, the spring elastic force ensures that the column head 13 is quickly reset, preventing the column head 13 from loosening or concrete from penetrating into the pipe body during the vibration process, and the channel forming completeness rate is high.

[0072] 2. The device can be integrated into the traditional template system without the need for additional large-scale equipment. It is compatible with existing processes and has a low threshold for transformation. By adjusting the pressure of the second airbag 16 and the parameters of the column head 13, it is applicable to various working conditions, compatible with existing processes, and has a wide range of applicability.

[0073] This embodiment also proposes a construction process for controlling cracks in a gravity dam based on constructing a strain gradient, and uses a construction device for controlling cracks in a gravity dam based on constructing a strain gradient, including the following steps:

[0074] S1. Construction preparation: diversion, site leveling, and material preparation;

[0075] 1-1. Diversion Project: Select a diversion scheme (phased cofferdam / full cofferdam) based on hydrological conditions, and complete the construction of upstream and downstream cofferdams, diversion tunnels / open channels;

[0076] 1-2. Site preparation: Level the dam foundation 1 and the working area, build a mixing station, transportation channels, water and power supply systems, and complete raw material inspection and concrete mix design.

[0077] S2. Foundation treatment: excavation of dam foundation 1, bedrock treatment and grouting;

[0078] 2-1. Excavation of dam foundation 1: Use blasting / mechanical excavation to remove the overburden and weathered rock to the designed foundation surface, and use anchor spraying to support the slope to ensure stability;

[0079] 2-2. Bedrock treatment and grouting: After excavation to fresh bedrock and cleaning and acceptance, 5-8 meter deep holes are drilled in the dam foundation for consolidation grouting to enhance the integrity; deep holes are drilled at the heel of the dam for curtain grouting to form an anti-seepage barrier.

[0080] S3. Install formwork reinforcement: erect formwork and tie reinforcement;

[0081] 3-1. Set up the steel formwork, calibrate the verticality, and seal the joints to prevent leakage; tie the steel bars according to the drawing, control the spacing and thickness of the protective layer, and ensure the joints are compliant.

[0082] 3-2. Layout of cooling water system: Lay cooling water pipes on the inner side of the formwork and between the steel skeleton and fix them with steel brackets; connect the inlet and outlet of the cooling water pipes to the external water main of dam body 2, install temperature control valves and flow sensors, and bury temperature monitoring elements simultaneously.

[0083] S4. Install the outer tube assembly: Position and install the outer tube assembly at the designed position; during construction, position and install the outer tube assembly according to the axis hole position; after installation, place the uninflated second airbag 16 into the installation space surrounded by the strip plate 11, and then inflate the second airbag 16. The second airbag 16 inflates and bulges, squeezing the end plate 15. The end plate 15 compresses the compression spring 14, and the column head 13 extends through the through hole 12.

[0084] S5. Concrete pouring: pouring in blocks and layers, temperature-controlled vibration, and curing;

[0085] 5-1. Layering and Blocking: The dam body 2 is usually divided along the axis and layered vertically, using the through-casting or columnar casting method;

[0086] 5-2. Transport to warehouse: Use tower crane bucket or cable crane to transport concrete, the free fall height into the warehouse is ≤2m, and the temperature of the warehouse is controlled;

[0087] 5-3. Vibration curing: The inserted vibrator should be ≥30cm away from the hole-making device, and vibrate until the slurry is overflowing and free of bubbles; after initial setting, cover with heat-insulating and moisture-retaining materials, and the curing period should be ≥28 days.

[0088] After pouring the concrete, the column head 13 exposed outside the second tube body 10 is buried in the concrete.

[0089] S6. Cavity 4 construction: After the concrete is initially set, the outer tube assembly is pulled out to form a cavity 4 with an uneven interface. This interface is recorded as the outer occlusal boundary.

[0090] The specific construction method is:

[0091] During construction, the uninflated second airbag 16 is placed in the installation space of the strip board 11. Subsequently, the second airbag 16 is inflated. The second airbag 16 is inflated and bulges, squeezing one end of the column head 13. The compression spring 14 is compressed, and the other end of the column head 13 extends through the through hole 12. After pouring concrete, the column head 13 exposed outside the second tube body 10 is buried in the concrete.

[0092] After the concrete has initially set, the second airbag 16 is deflated and the second airbag 16 becomes deflated. The column head 13 moves backward into the second tube body 10 under the elastic force of the compression spring 14. After the column head 13 withdraws, a recessed portion 5 is formed in the concrete. Subsequently, the second airbag 16 and the second tube body 10 are pulled out to form a cavity 4 with a hole array.

[0093] When to Pull Out: After the concrete has initially set, use the pulling equipment to lift the concrete. Monitor the resistance during the process and immediately pause and make adjustments if any stalling is detected. Pulling out after initial setting ensures that the shape of the cavity 4 is essentially stable—that is, the concrete has sufficient strength to support the hole walls—while also allowing for relatively easy extraction of the device to form the recessed portion 5 before the concrete's plasticity has completely disappeared, thus avoiding damage to the hardened concrete.

[0094] S7. After checking that the cavity 4 meets the design requirements, the inner tube assembly is coaxially positioned and installed inside the cavity 4; the specific method is: after the second tube body 10 is demolded, a positioning boss 41 is formed at the bottom of the cavity 4, the bottom end of the first tube body 6 is inserted into the cavity 4 and fixed with the positioning boss 41, and the centering limit is forced at the bottom of the cavity 4; subsequently, the top of the first tube body 6 is fixed to form a top limit to ensure the coaxiality of the first tube body 6 and the cavity 4.

[0095] Using positioning boss 41 as a prefabricated physical reference, first tube 6 can be quickly positioned through direct insertion, eliminating the complex steps of "measurement and alignment → temporary fixation → review and adjustment" in traditional processes. This ensures coaxiality and installation accuracy, thereby preventing strain gradient uniformity and reduced crack control effectiveness. Furthermore, the mechanical lock formed by the insertion structure between positioning boss 41 and the bottom end of first tube 6 resists external disturbances such as concrete vibration and pipe pulling forces, preventing displacement and eccentricity.

[0096] S8. Filling the outer layer stress absorbing material 31: Fill the outer layer stress absorbing material 31 in the area between the cavity 4 and the inner tube assembly. The outer layer stress absorbing material 31 is connected to the inner wall of the cavity 4 as a whole, and a mosaic structure is formed at the boundary.

[0097] The chimeric interface designed in this step enables the outer layer stress-absorbing material 31 and the concrete to form a "rigid-flexible" composite system. The concrete provides structural rigidity, and the outer layer stress-absorbing material 31 is tightly connected to the concrete through the chimeric interface, thereby compensating for the defects of "high rigidity and low ductility" of the concrete. When the concrete is deformed due to temperature changes or loads, the concave and convex structure of the chimeric interface can limit the relative slip between the stress-absorbing material and the concrete through mechanical bite, making the stress transfer more uniform and avoiding stress concentration at the interface.

[0098] S9. After the outer layer stress absorbing material 31 is initially solidified, the inner tube assembly is pulled out to form a central hole 9 with a spiral groove interface. This interface is recorded as the inner layer bite boundary.

[0099] The specific method for removing the inner tube assembly is as follows:

[0100] The top of the first spring hose 7 is disassembled from the first tube body 6, and the first tube body 6 is lifted. The first tube body 6 can slide relative to the first spring hose 7, and the first tube body 6 can also slide relative to the first spring hose 7; since the bottom end of the first spring hose 7 is fixedly connected to the bottom end of the first tube body 6, as the first tube body 6 moves upward, the first tube body 6 simultaneously pulls the first spring hose 7 to move, and the first spring hose 7 is pulled out of the concrete;

[0101] As the first tube body 6 continues to move upward, the first spring hose 7 is continuously separated from the concrete, and a spiral groove is formed after the separation; when the first tube body 6 is completely pulled out, the central hole 9 with the spiral groove is formed.

[0102] In this step, the first spring hose 7 is driven by the cooperative mechanism of the first tube body 6, and there is no need to disassemble the first tube body 6 and the first spring hose 7 in stages. The first spring hose 7 can be driven to be pulled out synchronously by lifting the first tube body 6, which reduces the time cost of step-by-step operation, shortens the overall construction period, and improves construction continuity.

[0103] The first spring hose 7 is withdrawn from the bottom to the top. When withdrawing from the bottom, the bottom end of the first spring hose 7 is fixed to the tube body. During the upward movement, the tension is evenly transferred from the bottom to the top, gradually separating the first spring hose 7 from the concrete along a spiral trajectory. This method avoids channel distortion and deformation caused by a mismatched withdrawal sequence, ensuring the quality of the spiral groove. If withdrawn from the top first, the bottom concrete may lose support due to premature hollowing of the upper channel, which can lead to collapse, especially when the concrete is not fully set. Withdrawing from the bottom upwards, however, reduces the possibility of localized voids or collapse.

[0104] Extraction begins at the bottom, with the bottom end of the first spring hose 7 fixed. As the system pulls upward, the tension is evenly distributed axially. If extraction is performed from the top, the bond between the concrete at the bottom and the first spring hose 7 may be concentrated, leading to sudden localized stress changes and potentially causing the channel to fracture. However, extracting from the bottom to the top allows the first spring hose 7 to gradually detach from the concrete, reducing instantaneous peak tension and maintaining the integrity of the channel. When the concrete initially sets, extracting from the bottom first releases the constraints of the surrounding concrete in a "bottom-up" sequence. This bottom-to-top extraction sequence is less sensitive to construction speed. Even with slight fluctuations in extraction speed, the uniform distribution of tension results in a more gradual change in the spiral groove's morphology, making the construction operation more fault-tolerant.

[0105] S10. Fill the center hole 9 with an inner layer of stress absorbing material 32. After filling, an interlocking interface is formed between the inner layer of stress absorbing material 32 and the outer layer of stress absorbing material 31. At the same time, a concentric strain gradient structure 3 is constructed in the cavity 4. Multiple cavities 4 form a distributed stress absorbing hole group with a strain gradient.

[0106] In this embodiment, the outer layer stress absorbing material 31 and the inner layer stress absorbing material 32 can be selected from the following materials: rubber concrete, rubber asphalt mortar, acrylic concrete, acrylic rubber concrete, acrylic mortar, acrylic rubber mortar, epoxy asphalt mortar, fiber reinforced rubber concrete, and fiber reinforced acrylic mortar.

[0107] The stress-absorbing material in the above embodiment is a type of engineering material with high elasticity, low stiffness, and good energy absorption capacity. It has the characteristics of low modulus, high ductility, and good adhesion. Through its own deformation or internal damping, it absorbs and dissipates the stress generated by the dam under temperature changes, shrinkage, and load, inhibits the initiation and expansion of cracks, and improves the durability of the structure.

[0108] The core functions of stress absorbing materials:

[0109] First, stress buffering: absorbing energy (such as temperature stress and uneven foundation settlement stress) through elastic deformation; second, crack control: reducing interface stress concentration and delaying the crack expansion path; third, collaborative work: forming a composite system with ordinary concrete to improve the overall deformation coordination.

[0110] Application results:

[0111] First, the construction device designed in the present invention forms an outer bite boundary and an inner bite boundary at the interface after the tube is pulled out, so that bite interfaces are formed between the outer stress absorbing material 31 and the concrete, and between the outer stress absorbing material 31 and the inner stress absorbing material 32, respectively, thereby increasing the interface roughness and contact area, enhancing the overall synergistic effect, and significantly improving the shear strength through mechanical bite. Compared with a straight interface, it can effectively inhibit interlayer slip cracking and effectively improve the interface mechanical properties.

[0112] Secondly, the present invention adopts a staged tube removal and filling process to ensure that the stress absorbing material is clearly layered and has high density, avoids mixing or uneven filling, and ensures that the strain gradient is accurately formed.

[0113] Third, this process creates a strain-gradient active stress absorption system. Two layers of material form a gradient, gradually absorbing strain. This gradient distribution of material properties avoids the concentrated cracking caused by sudden stress changes in traditional structures. Instead, strain is gradually released radially, reducing the probability of crack initiation. The strain-gradient structure 3 fundamentally reduces stress levels through material deformation and interfacial energy dissipation, resulting in more significant crack resistance, adaptability to dynamic loads and environmental changes, and enhanced structural durability.

[0114] In addition, in this embodiment, the connection interface between the outer layer stress absorbing material 31 and the inner layer stress absorbing material 32 is designed to be a spiral groove interlocking combination. The purpose of this design is:

[0115] When a gravity dam is subjected to temperature changes, foundation settlement, and other effects, the stress direction becomes random (e.g., a combination of tension, compression, and shear). The spatial curve of the spiral groove can effectively deform under horizontal, vertical, and oblique loads, absorbing energy in different directions through the elastic twisting and extrusion of the spiral structure. Compared to a flat interface, a flat surface can only resist tension and compression in the vertical direction and has a weaker resistance to shear loads. However, the spiral groove can dissipate shear energy through "spiral torsion," achieving better results. Compared to a flat interface, the spiral groove increases the contact area. The larger contact area can disperse concentrated stress into distributed stress along the spiral path, reducing local stress peaks at the interface and avoiding material damage caused by stress concentration.

[0116] The outer layer stress absorbing material 31 and the inner layer stress absorbing material 32 adopt a gradient design with small strain in the outer layer and large strain in the inner layer. The gradual interlocking of the spiral groove can form a smooth transition of strain from the outer layer to the inner layer, avoiding interface debonding caused by sudden changes in modulus. This gradient conduction mechanism allows the two layers of material to share the load more evenly and improve overall energy consumption efficiency. The spiral groove locks the two layers of material into a whole, but each layer can still consume energy independently through its own deformation. When the outer layer stress absorbing material 31 undergoes plastic deformation due to high stress, the spiral interface can transfer part of the stress to the inner layer material, forming a layered energy dissipation mechanism to avoid overload damage to a single material. For example: when the temperature drops suddenly, the outer layer stress absorbing material 31 first absorbs part of the stress through elastic compression, and the remaining stress is transferred to the inner layer through the spiral interface, which is further buffered by the high ductility of the inner layer stress absorbing material 32.

[0117] Example 2:

[0118] Based on the above embodiment, the outer wall of the second tube body 10 is wrapped with a second spring hose, which does not interfere with the column head 13. The second spring hose and the column head 13 are designed to form a composite interfacial structure of spiral grooves and hole arrays.

[0119] Once the outer layer of stress-absorbing material 31 is filled, the spiral grooves provide continuous friction and shear resistance in the axial direction (the primary direction of force applied to the dam body 2), preventing material slippage along the axis of the cavity 4. This is particularly effective in resisting axial stresses such as thermal deformation and dam body 2 settlement. The three-dimensional hole array, composed of recesses 5 formed by the column heads 13, creates a "mortise and tenon" fit in the radial direction of the outer layer of stress-absorbing material 31. The spiral grooves provide axial fit, while the hole array provides radial fit. This three-dimensional fit enhances overall bonding strength while allowing for deformation in various directions, thereby improving energy dissipation.

[0120] For example, after the concrete solidifies, the outer layer of stress-absorbing material 31 in the hole array is like a nail inserted into the concrete matrix to prevent radial cracking. The combination of the two forms a three-dimensional mechanical lock of axial thread and radial nail anchor, and the interface bonding strength can be effectively improved compared with a single structure.

[0121] Example 3:

[0122] Based on Example 1 or Example 2, the first spring hose 7 and / or the second spring hose are filled with a gas or liquid medium. Both ends of the first spring hose 7 and the second spring hose are sealed, and the liquid medium filled therein can be water or hydraulic oil. Valves are provided at the tops of the first spring hose 7 and the second spring hose for controlling the filling and draining of the liquid.

[0123] Taking the first spring hose 7 as an example, the advantages of filling it with gas or liquid are as follows:

[0124] The first spring hose 7 inherently has a certain degree of elasticity. When inflated, the internal air pressure causes the hose to expand, thereby increasing its radial stiffness. This allows the hose 7 to withstand external pressure during concrete pouring. The stiffness of the hose after being filled with gas or liquid can withstand this pressure and maintain its spiral shape. This provides greater stability than an unfilled first spring hose 7, especially in highly fluid concrete environments. This prevents the hose from being flattened or deformed, which could result in unclear spiral groove formation.

[0125] The above description is only a preferred embodiment of the present invention and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A gravity dam crack control construction device based on constructing a strain gradient, comprising an outer tube assembly and an inner tube assembly used in conjunction with the outer tube assembly, characterized in that: The inner tube assembly comprises a first tube body (6), the outer wall of which is wound with a first spring hose (7) in a spiral pattern; the bottom end of the first tube body (6) is open; The outer tube assembly comprises a second tube body (10), the bottom end of the second tube body (10) has a closed cover plate (8) and the top end is open; the center of the cover plate (8) has a positioning hole (81) recessed toward the top end of the second tube body (10), a positioning boss (41) is formed at the positioning hole (81) after concrete pouring, and the bottom end of the first tube body (6) can be positioned and plugged with the positioning boss (41); the second tube body (10) has at least one group of hole arrays on the tube wall, and the hole array includes a plurality of spaced through holes (12) arranged along the height direction of the second tube body (10); the second tube body (10) ) is provided with a vertical strip (11) in the internal cavity, and the strip (11) is fixedly connected to the inside of the second tube body (10); a plurality of column heads (13) that can be adapted to be plugged into the through hole (12) are provided on the strip (11), and the column heads (13) are slidably connected to the strip (11); a compression spring (14) is sleeved on the column head (13), one end of the compression spring (14) is connected to one end of the column head (13), and the other end is connected to the strip (11); when an external force presses one end of the column head (13), the column head (13) can move, and the other end of the column head (13) extends outward through the through hole (12); The outer tube assembly further comprises a second airbag (16), a mounting space is formed between the plurality of strips (11), and the second airbag (16) can be placed in the mounting space; the second airbag (16) is provided with an inflatable / deflated valve.

2. The construction device for controlling cracks in a gravity dam based on constructing a strain gradient according to claim 1, characterized in that: A sealing ring (17) is provided on the hole wall of the through hole (12), and the column head (13) can be connected to the sealing ring (17) in a sealing and sliding manner.

3. The construction device for controlling cracks in a gravity dam based on constructing a strain gradient according to claim 1, characterized in that: The column head (13) is cylindrical, conical or polygonal.

4. The construction device for controlling cracks in a gravity dam based on constructing a strain gradient according to claim 1, characterized in that: One end of the column head (13) is connected to an end plate (15), and one end of the compression spring (14) is connected to the end plate (15).

5. The construction device for controlling cracks in a gravity dam based on constructing a strain gradient according to claim 1, characterized in that: A second spring hose is wound around the outer wall of the second tube body (10), and the second spring hose and the column head (13) do not interfere with each other.

6. The construction device for controlling cracks in a gravity dam based on constructing a strain gradient according to claim 1, characterized in that: The first spring hose (7) and / or the second spring hose are filled with gas or liquid medium.

7. A construction process for controlling cracks in a gravity dam based on constructing a strain gradient, characterized by: The construction device for controlling cracks in a gravity dam based on constructing a strain gradient according to any one of claims 1 to 6 comprises the following steps: S1. Construction preparation: diversion, site leveling, and material preparation; S2. Foundation treatment: dam foundation (1) excavation, bedrock treatment and grouting; S3. Install formwork reinforcement: erect formwork and tie reinforcement; S4. Install the outer tube assembly: Position and install the outer tube assembly in the designed position; S5. Concrete pouring: pouring in blocks and layers, temperature-controlled vibration, and curing; S6. Construction of cavity (4): After the concrete has initially set, the outer tube assembly is pulled out to form a cavity (4) with an uneven interface, which is recorded as the outer occlusal boundary; S7. After checking that the cavity (4) meets the design requirements, the inner tube assembly is coaxially positioned and installed inside the cavity (4); S8. Filling the outer layer stress absorbing material (31): Filling the outer layer stress absorbing material (31) in the area between the cavity (4) and the inner tube assembly, the outer layer stress absorbing material (31) and the inner wall of the cavity (4) are connected as a whole, and a mosaic structure is formed at the boundary; S9. After the outer layer stress absorbing material (31) is initially solidified, the inner tube assembly is pulled out to form a central hole (9) with a spiral groove interface. This interface is recorded as the inner layer occlusal boundary; S10. Filling the center hole (9) with an inner layer of stress absorbing material (32), forming an interlocking interface between the inner layer of stress absorbing material (32) and the outer layer of stress absorbing material (31); at the same time, constructing a concentric circle strain gradient structure (3) in the cavity (4); and forming a distributed stress absorbing hole group with a strain gradient by a plurality of cavities (4).

8. The construction process for controlling cracks in a gravity dam based on constructing a strain gradient according to claim 7 is characterized in that: The method for constructing the S6 mesoporous cavity (4) is as follows: During construction, the uninflated second airbag (16) is placed in the installation space of the strip board (11), and then the second airbag (16) is inflated. The second airbag (16) is inflated and bulges, squeezing one end of the column head (13). The compression spring (14) is compressed, and the other end of the column head (13) extends through the through hole (12). After pouring concrete, the column head (13) exposed outside the second tube body (10) is buried in the concrete. After the concrete is initially set, the second airbag (16) is deflated, the second airbag (16) becomes deflated, and the column head (13) moves backward into the second tube body (10) under the elastic force of the compression spring (14); after the column head (13) is withdrawn, a recessed portion (5) is formed in the concrete; subsequently, the second airbag (16) and the second tube body (10) are pulled out to form a cavity (4) with a hole array.

9. The construction process for controlling cracks in a gravity dam based on constructing a strain gradient according to claim 7, characterized in that: The specific installation method of the inner tube assembly in S7 is as follows: After the second tube body (10) is demoulded, a positioning boss (41) is formed at the bottom of the cavity (4), and the bottom end of the first tube body (6) is inserted into the cavity (4) and fixedly connected to the positioning boss (41), forcing the centering limit at the bottom of the cavity (4); subsequently, the top of the first tube body (6) is fixed to form a top limit to ensure the coaxiality of the first tube body (6) and the cavity (4); The specific method for removing the inner tube assembly in S9 is as follows: The top of the first spring hose (7) is disassembled and separated from the first tube body (6), and the first tube body (6) is lifted up, so that the first tube body (6) can slide relative to the first spring hose (7), and the first tube body (6) can also slide relative to the first spring hose (7); since the bottom end of the first spring hose (7) is fixedly connected to the bottom end of the first tube body (6), as the first tube body (6) moves upward, the first tube body (6) simultaneously pulls the first spring hose (7) to move, and the first spring hose (7) is pulled out of the concrete; As the first tube body (6) continuously moves upward, the first spring hose (7) continuously separates from the concrete, and a spiral groove is formed after separation; when the first tube body (6) is completely pulled out, a central hole (9) with a spiral groove is formed.

Images