Crack control structure and method of concrete gravity dam based on stress absorption

Abstract

The present invention proposes a crack control structure and method for a concrete gravity dam based on stress absorption, which belongs to the field of crack control of concrete structures in water conservancy projects. The structure includes a dam body, which is provided with a plurality of cavities, which are arranged vertically along the height direction of the dam body; the inner wall of the cavity has a recessed portion, forming an uneven interface; the cavity is filled with stress-absorbing material, forming a stress-absorbing hole group; the stress-absorbing material is connected to the inner wall of the cavity and the recessed portion, and a mosaic structure is formed at the boundary. In the construction method, a hole-forming device is introduced, and a hole-forming device and process synchronized with the cast-in-place concrete construction are developed to ensure the forming accuracy and efficiency of the complex cavity structure. The present invention develops a stress absorption structure that can be integrated into the interior of the dam body, has strong interface bonding ability and is feasible for construction, constructs an active stress absorption system, and is suitable for crack prevention and control of large-volume concrete gravity dams, combining structural safety and construction economy.

Description

Technical Field

[0001] The present invention belongs to the field of crack control of concrete structures in water conservancy projects, and in particular relates to a crack control structure and method for a concrete gravity dam based on stress absorption. Background Art

[0002] Gravity dams, as key structures in water conservancy projects, play a vital role in regulating water resources, preventing floods and reducing disasters, and ensuring water supply for agricultural production and residents. Dam cracks have long been a key research focus and challenge for scholars both domestically and internationally. Existing technologies primarily utilize medium- and low-heat cements. By optimizing concrete mix proportions, reducing the amount of cementitious materials, adjusting aggregate gradations, and applying shrinkage compensation, these technologies reduce concrete temperature rise and the risk of cracking. From a construction perspective, concrete is constructed in compartments and layers, with cooling water pipes embedded within the concrete to lower mixing water temperature and pre-cool the aggregates. This reduces heat in the concrete, minimizes the internal and external temperature difference, improves temperature distribution, and reduces thermal stress. Concrete curing methods, such as intelligent spraying and covering insulation, reduce internal and external temperature differences in concrete. Research and practice have shown that these technical measures have, to a certain extent, reduced temperature and shrinkage stresses in dam concrete, mitigating the risk of dam cracking.

[0003] However, internal stress within the dam structure is the root cause of concrete cracks. Therefore, eliminating this internal stress is crucial for resolving cracks during construction and operation of concrete gravity dams. Existing research methods, whether reducing concrete thermal stress or shrinkage stress, have struggled to fundamentally eliminate internal stress within the dam, and suffer from insufficient internal stress regulation.

[0004] Therefore, how to optimize the stress distribution inside the dam, reduce stress concentration, and develop a stress-absorbing structure that can be integrated into the dam body, has strong interface bonding capabilities, and is feasible to construct, has become a key breakthrough direction for solving the problem of cracks in gravity dams. Summary of the Invention

[0005] Based on the problems existing in the background technology, the present invention proposes a stress-absorbing concrete gravity dam crack control structure and method. The purpose is to solve the problems of existing gravity dam crack control methods, such as insufficient internal stress regulation, easy interface debonding, and poor construction compatibility.

[0006] In order to solve the above problems, the following technical solutions are adopted:

[0007] First, the technical solution proposes a crack control structure for a concrete gravity dam based on stress absorption, comprising a dam body, with a plurality of cavities provided on the dam body, the cavities being arranged vertically along the height direction of the dam body; the inner wall of the cavity has a recessed portion, so that the wall surface of the cavity forms an uneven interface; the cavity is filled with stress absorbing material to form a stress absorbing hole group; the stress absorbing material is connected to the inner wall of the cavity and the recessed portion, forming a mosaic structure at the boundary.

[0008] Preferably, the cross-sectional shape of the cavity includes but is not limited to circular, rectangular, and polygonal.

[0009] Preferably, the stress absorbing material includes but is not limited to 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.

[0010] Preferably, the recessed portion is a hole, a groove or a spiral groove.

[0011] In a second aspect, this technical solution proposes a method for controlling cracks in a concrete gravity dam based on stress absorption, which is used to construct the aforementioned concrete gravity dam crack control structure based on stress absorption, and includes the following steps:

[0012] S1. Construction preparation: diversion, site leveling, and material preparation;

[0013] S2. Foundation treatment: dam foundation excavation, bedrock treatment and grouting;

[0014] S3. Install formwork reinforcement: erect formwork and tie reinforcement;

[0015] S4. Install the hole forming device: Position and install the hole forming device at the designed position;

[0016] S5. Concrete pouring: pouring in blocks and layers, temperature-controlled vibration, and curing;

[0017] S6. Hole Cavity Construction: After the concrete has initially set, remove the hole-forming device to form the cavity.

[0018] S7. Filling with stress absorbing material: After checking that the pores meet the design requirements, fill the pores with stress absorbing material to form a stress absorbing pore group.

[0019] Preferably, the hole-forming device in S4 includes a supporting body, at least the bottom end of which is closed; the outer wall of the supporting body is spirally wound with a spring hose, the bottom end of the spring hose is fixedly connected to the bottom outer wall of the supporting body; the top end of the spring hose is detachably connected to the top outer wall of the supporting body.

[0020] Preferably, the supporting body is a first tube body or a first airbag; the first tube body is a PVC tube or a steel tube; when the supporting body is the first airbag, the top of the first airbag is also a closed end, and the end has an air nozzle that can be inflated and deflated.

[0021] Preferably, the head end and the tail end of the spring hose are sealed, and gas is stored inside.

[0022] Preferably, the step of removing the pore forming device in S6 is as follows:

[0023] ① When the supporting body is the first tube, the method is as follows:

[0024] Disassemble and separate the top end of the spring hose from the top end of the first tube body;

[0025] The first tube body is lifted up, and the first tube body can slide along the cavity and relative to the spring hose. Since the bottom end of the 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 pulls the spring hose to move, thereby extracting the spring hose from the concrete.

[0026] As the first tube body continues to move upward, the 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 cavity with a spiral groove is formed;

[0027] ② When the supporting body is the first airbag, the method is as follows:

[0028] Deflate the first airbag;

[0029] After the first airbag is deflated, it no longer supports the spring hose, and the first airbag is directly pulled upward. The first airbag and the spring hose are pulled out, and the cavity with the spiral groove is formed.

[0030] Preferably, the hole-forming device in S4 has the following structure, including a second tube body, the bottom end of the second tube body is closed and the top end is open; the second tube body is provided with at least one group of hole arrays on the tube wall, and the hole array includes a plurality 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 interior of the second tube body; a plurality of column heads that can be adapted to be 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 an 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.

[0031] The above technical solution has the following advantages:

[0032] 1. The present invention constructs an active stress absorption system, transforming crack control from passive repair to active prevention. By setting up a vertical cavity network inside the dam body and filling it with low-modulus elastic-plastic stress-absorbing material to form a distributed stress-absorbing hole group, the internal stress of the dam body is effectively absorbed, and the directional reduction of the internal stress peak of the dam body is achieved, providing a key technical means for solving the crack problem during the construction and operation of concrete gravity dams.

[0033] 2. A recessed portion is constructed on the inner wall of the cavity, allowing the filled stress-absorbing material to form a mechanically interlocking interface with the concrete. This improves the reliability of the bond between the stress-absorbing material and the concrete, ensuring efficient stress transfer and preventing debonding failure, ensuring collaborative operation throughout the dam's lifecycle. The interlocking structure prevents interlayer slippage, blocking the path for crack propagation and synergizing the stress absorption of the stress-absorbing material with the load-bearing function of ordinary concrete. This interlocking structure addresses the core drawbacks of straight interfaces (deformation, bonding, and insufficient crack resistance). While it increases construction complexity, it significantly improves crack control effectiveness and is more adaptable to the complex stresses of the dam.

[0034] 3. This invention develops a hole-forming device and process that synchronizes with cast-in-place concrete construction, ensuring precision and efficiency in forming complex cavity structures. The dedicated hole-forming device achieves a high pass rate by forming recessed cavities in one step. Furthermore, the process is seamlessly integrated into the cast-in-place process, effectively shortening construction time and reducing overall costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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.

[0036] Figure 1 It is a cross-sectional view of the crack control structure of the concrete gravity dam based on stress absorption.

[0037] Figure 2 yes Figure 1 A magnified cross-sectional view of a single cavity before filling with stress-absorbing material.

[0038] Figure 3 It is a schematic diagram of the structure of the spring hose wrapped around the tube body.

[0039] Figure 4 It is a schematic diagram of the structure in which the spring hose is wrapped around the first airbag.

[0040] Figure 5 It is a three-dimensional diagram of the structure of the spring hose.

[0041] Figure 6 It is a structural diagram of plastic reinforced spiral pipe.

[0042] Figure 7It is a structural cross-sectional view of a pore-forming device in another embodiment.

[0043] Figure 8 yes Figure 7 Top view of the mid-hole forming device before it is cut open.

[0044] Figure 9 This is an enlarged schematic diagram of the structure of area A.

[0045] Figure 10 It is a process flow chart of the present invention.

[0046] Description of reference numerals:

[0047] 1. Dam foundation; 2. Dam body; 3. Stress absorbing material; 4. Cavity; 5. Recessed portion; 6. First tube body; 7. Spring hose; 8. Plastic reinforced spiral tube; 9. First airbag; 10. Second tube body; 11. Strip; 12. Through hole; 13. Column head; 14. Compression spring; 15. End plate; 16. Second airbag; 17. Sealing ring. DETAILED DESCRIPTION

[0048] 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.

[0049] Example 1:

[0050] like Figure 1 - Figure 2 As shown, this embodiment proposes a concrete gravity dam crack control structure based on stress absorption, including a dam body 2, which is arranged on a dam foundation 1; a plurality of cavities 4 are provided on the dam body 2, and the cavities 4 are vertically arranged along the height direction of the dam body 2; the inner wall of the cavity 4 has a recessed portion 5, so that the wall surface of the cavity 4 forms an uneven interface; the cavity 4 is filled with stress absorbing material 3 to form a stress absorbing hole group; the stress absorbing material 3 is connected to the cavity 4 and the inner wall of the recessed portion 5 as a whole, forming a mosaic structure at the boundary.

[0051] In this embodiment, the cross-sectional shape of the cavity 4 includes, but is not limited to, circular, rectangular, polygonal, or irregular shapes. The recessed portion 5 may be a hole, a groove, or a spiral groove. The groove may be one or more of a rectangular groove, an annular groove, a toothed groove, a wavy groove, a polygonal groove, or an irregular groove.

[0052] The stress absorbing material 3 includes but is not limited to 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.

[0053] The stress-absorbing material 3 in this 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.

[0054] The core functions of stress absorbing material 3 are: 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 propagation path; third, collaborative work: forming a composite system with ordinary concrete to improve the overall deformation coordination.

[0055] In this embodiment, an active stress absorption system is constructed, and the concept of "stress absorption hole group" is introduced into the main structure of the gravity dam. It serves as an active, distributed stress release / absorption unit, rather than passive bearing or post-processing. Crack control is changed from passive repair to active prevention. By setting a vertical hole 4 network inside the dam body 2 and filling it with low-modulus elastic-plastic stress absorption material 3 to form a distributed stress absorption hole group, the internal stress of the dam body 2 is effectively absorbed, and the directional reduction of the stress peak inside the dam body 2 is achieved.

[0056] In this embodiment, the "recess 5" and "interlocking structure" do not simply fill the hole. Instead, by designing the concave and convex shapes of the inner wall of the cavity 4, they significantly increase the contact area and interfacial fit between the stress-absorbing material 3 and the concrete of the dam body 2. This mechanical interlocking effect greatly enhances their ability to work together, prevents debonding, and ensures that stress is effectively transferred to the stress-absorbing material 3. This interface resists interlayer slip through an "interlocking effect," improving interfacial bond strength and deformation coordination, making it more adaptable to the complex stresses of the dam.

[0057] Example 2:

[0058] like Figure 3-Figure 5 As shown and Figure 10 As shown, this embodiment proposes a method for controlling cracks in a concrete gravity dam based on stress absorption, which is used to construct the concrete gravity dam crack control structure based on stress absorption in Example 1, and includes the following steps:

[0059] S1. Construction preparation: diversion, site leveling, and material preparation;

[0060] 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;

[0061] 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.

[0062] S2. Foundation treatment: excavation of dam foundation 1, bedrock treatment and grouting;

[0063] 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;

[0064] 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.

[0065] S3. Install formwork reinforcement: erect formwork and tie reinforcement;

[0066] 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.

[0067] 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 the dam body, install temperature control valves and flow sensors, and bury temperature monitoring elements simultaneously.

[0068] S4. Install the hole forming device: Position and install the hole forming device at the designed position;

[0069] 4-1. Locate the hole position according to the axis and position and install the hole cutter.

[0070] S5. Concrete pouring: pouring in blocks and layers, temperature-controlled vibration, and curing;

[0071] 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;

[0072] 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;

[0073] 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.

[0074] S6. Cavity 4 construction: After the concrete is initially set, pull out the hole forming device to form cavity 4;

[0075] 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.

[0076] S7. Filling with stress absorbing material 3: After removing the tube, promptly check the integrity of the channel. After checking that the cavity 4 meets the design requirements, fill the cavity 4 with stress absorbing material 3 to form a stress absorbing hole group.

[0077] It should be noted that the holes 4 in the present invention can be arranged in single rows, multiple rows, or staggered. Arranging a single row of stress-absorbing holes along a specific direction within the dam is suitable for areas with relatively small stress concentrations. Arranging multiple rows of stress-absorbing holes along multiple directions within the dam forms a stress-dispersing network, which is suitable for areas with larger stress concentrations. To prevent mutual interference between stress-absorbing holes, staggering the holes improves stress dispersion.

[0078] In this embodiment, the pore forming device has various structural forms, which are described in detail below:

[0079] The hole-forming device in S4 includes a supporting body, at least the bottom end of which is closed; the outer wall of the supporting body is spirally wound with a spring hose 7, and the bottom end of the spring hose 7 is fixedly connected to the bottom outer wall of the supporting body; the top end of the spring hose 7 is detachably connected to the top outer wall of the supporting body, and is convenient to disassemble when disassembly is required.

[0080] In this embodiment, the supporting body has two structural forms:

[0081] The supporting body is the first tube 6 or the first airbag 9:

[0082] When the supporting body is the first tube body 6, the first tube body 6 is a PVC tube or a steel tube;

[0083] When the supporting body is the first airbag 9 , the top of the first airbag 9 is also a closed end, and the end is provided with an air nozzle capable of inflating and deflation.

[0084] The steps for removing the hole forming device in S6 are as follows:

[0085] ① When the supporting body is the first tube 6, the method is as follows:

[0086] Disassemble and separate the top end of the spring hose 7 from the top end of the first tube body 6;

[0087] When the first tube body 6 is lifted, the first tube body 6 can slide along the cavity and can also slide relative to the spring hose 7. Since the bottom end of the 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 spring hose 7 to move, thereby pulling the spring hose 7 out of the concrete.

[0088] As the first tube body 6 continues to move upward, the 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 cavity 4 with the spiral groove is formed;

[0089] ② When the supporting body is the first airbag 9, the method is as follows:

[0090] Deflate the first airbag 9;

[0091] After the first airbag 9 is deflated, it no longer supports the spring hose 7 and the first airbag 9 is directly pulled upward. The first airbag 9 and the spring hose 7 are pulled out, and the cavity 4 with the spiral groove is formed.

[0092] The hole-forming device proposed in this embodiment adopts the structure of PVC pipe / steel pipe / first airbag 9+spring hose 7, which has a simple structure. The materials used (PVC pipe, steel pipe, spring hose 7, airbag) are all conventional engineering materials, and there are no technical obstacles in manufacturing; the construction process is inflation-pouring-deflation-tube extraction, which is easy to implement, does not require special equipment, has a simple process, and is easy for workers to operate.

[0093] Application results:

[0094] First, the construction is convenient: after the first airbag 9 is deflated, the spring hose 7 can be quickly pulled out without mechanical twisting or complicated disassembly;

[0095] Second, structural adaptability: the shape and size of the spiral groove can be flexibly controlled by adjusting the winding density and pitch of the spring hose 7;

[0096] Third, cost-effectiveness: the first airbag 9 and the spring hose 7 can be reused, which significantly reduces template loss.

[0097] Example 3:

[0098] On the basis of Example 2, the head and tail ends of the spring hose 7 are sealed, and gas is stored inside. An air valve is provided at the top of the spring hose 7 to control the inflation and deflation of gas. The reason for this arrangement is that the spring hose 7 itself has a certain elasticity, and the internal air pressure after inflation will cause the hose to expand, thereby increasing the radial rigidity. In this way, when pouring concrete, the spring hose 7 is subjected to external pressure, and the hardness after inflation can resist this pressure and maintain the spiral shape. This is more stable than the non-inflated spring hose 7, especially when the concrete fluidity is high, to prevent the hose from being flattened or deformed, resulting in unclear spiral groove formation.

[0099] Furthermore, when the spring hose 7 is not inflated, a gap easily forms between the spring hose 7 and the first airbag 9, preventing a tight fit. Concrete can seep into the gap, making extraction difficult and affecting the surface quality of the channel. However, when the spring hose 7 is inflated, it adheres tightly to the surface of the first airbag 9, eliminating the gap and forming a rigid spiral support layer. During concrete pouring, the internal pressure counteracts the external pressure, preventing radial contraction or spiral deformation of the hose due to pressure.

[0100] In this embodiment, the stiffness of the spring hose 7 is dynamically adjusted by inflation, thereby solving the contradiction of the traditional template being "flexible and easy to deform, but rigid and difficult to disassemble", significantly improving the molding quality and construction efficiency of the spiral groove, and being simple and practical.

[0101] Example 4:

[0102] like Figure 6 As shown, the hole-forming device can also be replaced by the following structure. The hole-forming device can use a plastic reinforced spiral tube 8. The top and bottom ends of the plastic reinforced spiral tube 8 are closed, and a water inlet valve and an exhaust valve (not shown in the figure) are provided at the top. When in use, water of a certain pressure is filled into the plastic reinforced spiral tube 8. After being filled with water, the radial support stiffness of the plastic reinforced spiral tube 8 is significantly improved, which can effectively resist the lateral pressure during concrete pouring.

[0103] The structure of the plastic reinforced spiral tube 8 is adopted, and the double-layer component of "the first air bag 9 + the spring hose 7" is cancelled. A single water-filled plastic reinforced spiral tube 8 is directly used, which effectively reduces the installation process and is more convenient to operate.

[0104] When removing the tube, a twisting and pulling method can be used. The core principle is to use the geometric properties of the spiral ribs to convert the rotational torque into an axial demolding force. This method is particularly suitable for demolding spiral structure channels. The spiral ribs of the plastic reinforced spiral tube 8 can be regarded as incomplete threads. During rotation, the meshing surface formed by the rib teeth and the concrete generates an axial component of force, similar to the principle of loosening a screw. In this embodiment, the spiral plastic ribs of the plastic reinforced spiral tube 8 are inherently torsion-resistant, which provides favorable conditions for construction operations.

[0105] Example 5:

[0106] like Figure 7-Figure 9 As shown, another structural form of a hole-forming device is also proposed in this embodiment. The hole-forming device in the above embodiment is mainly used to realize the construction of the spiral groove. Then, for the form in which the recessed portion 5 is a hole-shaped structure, the hole-forming device proposed in this embodiment can be used, specifically as follows:

[0107] The hole-forming device includes a second tube body 10, which has a closed bottom end and an open top end; the second tube body 10 is provided with 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 hole arrays are distributed circumferentially along the second tube body 10, and can be two groups, three groups, four groups or more groups; in this embodiment, two groups are provided as an exemplary reference. A vertical slat 11 is positioned within the interior cavity of the second tube 10 and is fixedly connected to the interior of the second tube 10. Several studs 13 are positioned on the slat 11, adapted to engage with the through-holes 12. These studs 13 are arranged along the height of the slat 11. Each stud 13 is slidably connected to the slat 11, forming a telescopic structure. A compression spring 14 is sleeved over the stud 13, one end of which is connected to one end of the stud 13 and the other end to the slat 11. In this embodiment, to facilitate the installation of the compression spring 14, one end of the stud 13 is also connected to an end plate 15, against which one end of the spring rests. When an external force compresses one end of the stud 13, the stud 13 is displaced, and the other end of the stud 13 extends outward through the through-hole 12. Initially, the stud 13 is concealed within the second tube 10, creating a concealed design.

[0108] In this embodiment, in order to facilitate the extrusion of the column head 13, a second air bag 16 is used. The second air bag 16 is an elongated cylindrical structure, and an installation space is formed between the multiple strips 11. When in use, the uninflated second air bag 16 is placed in the installation space of the strips 11, and then the second air bag 16 is inflated. The second air bag 16 is inflated and bulges, 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 air bag 16 is deflated, and the second air bag 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, and the second air bag 16, the second tube body 10, etc. are subsequently pulled out to form a cavity with a recessed portion 5 with a hole pattern.

[0109] The hole-forming device realizes the formation of regular hole-shaped recessed portions 5 in concrete components through the structural design of "second airbag 16 driving column head 13 to expand and contract + spring reset". Its application results include:

[0110] First, it can accurately form holes with controllable shapes: the hidden column head 13 design avoids interference with concrete pouring: In the initial state, the column head 13 is hidden within the second tube body 10, and the surface is smooth during concrete pouring, preventing the column head 13 from prematurely contacting the concrete, causing jamming or deformation, and ensuring dense concrete filling. After the second airbag 16 is inflated, the column head 13 synchronously and stably extends through the through hole 12, forming a regular protruding structure. After the concrete initially sets, the column head 13 retracts, leaving a precise recessed portion 5 with a consistent aperture and depth. Second, the hole array layout is flexible and adaptable to diverse needs: the hole array can be arranged in multiple groups (such as 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, linear holes, annular hole groups, and customized hole shapes (such as honeycomb and tooth structures) can be formed to meet the functional opening requirements of different gravity dams.

[0111] Secondly, after the second airbag 16 is inflated, it can evenly squeeze all the studs 13 through air pressure, achieving simultaneous extension of multiple studs 13, eliminating the need for manual adjustment of each one. This significantly shortens the assembly and positioning time of the hole-forming device, making it particularly suitable for drilling large areas and multiple holes. After the concrete initially sets, the second airbag 16 deflates, and the studs 13 quickly retract into the tube body under the elastic force of the compression spring 14, preventing the studs 13 from being trapped in the concrete and forming "barbs." This reduces friction and adhesion during tube extraction, significantly improving demolding efficiency, and preventing concrete damage or hole wall cracking caused by forced tube extraction.

[0112] Thirdly, positioning accuracy is high: the stud 13 is slidably connected to the strip 11 and held in place by a compression spring 14. During inflation, the second airbag 16 provides constant squeezing pressure, ensuring a consistent extension of the stud 13. During retraction, the spring tension is stable, preventing the stud 13 from getting stuck or rebounding out of position, ensuring accurate hole dimensions. Reusability: The strip 11, stud 13, and second airbag 16 components are independently removable and replaceable. The second tube 10 is constructed of a wear-resistant material (such as PVC, metal, high-strength HDPE, or a steel-plastic composite tube), and the second airbag 16 is constructed of age-resistant rubber. The entire device is reusable multiple times, reducing construction costs.

[0113] Fourthly, it is suitable for various concrete working conditions: it can be adapted to cast-in-place concrete applications in gravity dams. Gravity dam vibration operations require high vibration frequencies. The device utilizes a dual position limiter (14) and a second airbag (16). After inflation, the column head (13) extends and locks, with the compression spring (14) providing rigid support to resist displacement caused by the vibration force. After deflation, the spring force ensures the column head (13) quickly returns to its original position, preventing loosening of the column head (13) or concrete infiltration during vibration, ensuring a high degree of channel formation integrity. The device can be integrated into conventional formwork systems without the need for additional large-scale equipment. By adjusting the pressure of the second airbag (16) and the parameters of the column head (13), it is compatible with existing processes, offering a low barrier to retrofit and widespread applicability.

[0114] It should be noted that, in this embodiment, in order to ensure good sealing between the column head 13 and the through hole 12, a sealing ring 17 is installed on the hole wall of the through hole 12, and the column head 13 can be sealed and slidably connected with the sealing ring 17 to prevent concrete slurry from entering the second tube body 10.

[0115] During the pouring and vibrating of gravity dam concrete, traditional non-sealed structures can easily cause cement slurry to seep into the second tube body 10 through the gap between through-hole 12 and column head 13, causing problems such as column head 13 jamming and spring rust and failure. Sealing ring 17, made of silicone rubber or fluororubber, completely blocks the infiltration of concrete slurry, ensuring that the column head 13's telescopic mechanism remains in a clean environment and achieving a high pass rate for hole formation.

[0116] In addition, in some embodiments, the inner side of the sealing ring 17 can be 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.

[0117] 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 method for controlling cracks in concrete gravity dams based on stress absorption, characterized in that: The steps involved are as follows: 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 hole forming device: Position and install the hole forming device at the designed position; S5. Concrete pouring: block and layer pouring, temperature control, vibration and curing; after pouring the concrete, the column head (13) exposed outside the second tube (10) is buried in the concrete; S6. Construction of cavity (4): After the concrete begins to set, the hole-forming device is pulled out to form the cavity (4); S7. Filling the stress absorbing material (3): After checking that the cavity (4) meets the design requirements, the stress absorbing material (3) is filled into the cavity (4) to form a stress absorbing hole group; The hole forming device comprises a second tube body (10), the bottom end of the second tube body (10) is closed and the top end is open; the second tube body (10) is provided with at least one group of hole arrays on the tube wall, the hole array comprising a plurality of spaced through holes (12) arranged along the height direction of the second tube body (10); a vertical strip plate (11) is provided in the internal cavity of the second tube body (10); the strip plate (11) is fixedly connected to the inside of the second tube body (10); the strip plate (11) A plurality of column heads (13) are provided on the column head (13) that can be adapted to be plugged into the through hole (12), and the column heads (13) are slidably connected to the strip plate (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 plate (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); An installation space is formed between the plurality of strips (11); when in use, an uninflated second airbag (16) is placed in the installation space of the strips (11), and then the second airbag (16) is inflated. The second airbag (16) is inflated 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). After the concrete is initially set, the second airbag (16) is deflated, and the second airbag (16) becomes deflated. Under the elastic force of the compression spring (14), the column head (13) moves backward into the second tube body (10); 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 recessed portion (5) in a hole pattern.

2. The method for controlling cracks in concrete gravity dams based on stress absorption according to claim 1, characterized in that: The stress absorbing material (3) includes but is not limited to 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.

3. The method for controlling cracks in concrete gravity dams based on stress absorption according to claim 1, characterized in that: The cross-sectional shape of the cavity (4) includes but is not limited to circular, rectangular, and polygonal.

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