A crack-resistant structure for the upstream face of a concrete gravity dam in cold regions

Abstract

This application provides a crack-prevention structure for the upstream face of a concrete gravity dam in cold regions, relating to the field of concrete dam crack prevention technology. It includes a GRC composite extruded polystyrene board installed on the upstream face, horizontal pre-reserved joints located at areas of high vertical stress in the dam body, an asphalt resin isolation layer within the horizontal pre-reserved joints, and a water-stopping system at the horizontal pre-reserved joints. The water-stopping system is integrated with the water-stopping system of the dam body's transverse joints to form a double continuous seepage prevention system. The depth of the horizontal pre-reserved joints is the distance from the upstream face to the second water-stopping layer of the dam's transverse joints. Crack-limiting steel mesh is provided around the horizontal pre-reserved joints and behind the water-stopping system. This application achieves highly efficient crack prevention and seepage prevention on the upstream face of a gravity dam in cold regions through the synergistic effect of insulation, protection, stress release, and multiple water-stopping and crack-limiting structures. The crack prevention effect is significant, greatly improving the crack resistance and long-term service life of the upstream face of the gravity dam in cold regions.

Description

Technical Field

[0001] This application relates to the field of concrete dam crack prevention technology, and in particular to a crack prevention structure for the upstream face of a concrete gravity dam in a cold region. Background Technology

[0002] The upstream face of a concrete gravity dam in a cold region is subjected to long-term low-temperature attack, freeze-thaw cycle, reservoir water level changes and water flow scouring. The temperature difference between the inside and outside of the dam concrete is large and the temperature drop shrinkage stress is highly concentrated, which makes it very easy to produce surface cracks, deep cracks and even penetrating cracks. Among them, transverse cracks caused by temperature stress along the dam axis (horizontal direction) and horizontal cracks caused by vertical temperature stress seriously damage the integrity of the dam structure, seepage prevention performance and long-term durability.

[0003] Current conventional dam surface insulation measures mostly use a single insulation board or a simple protective layer. Although such measures can reduce surface heat loss to a certain extent, they generally have defects such as weak resistance to ice pull-out, poor resistance to water flow erosion, and easy detachment after ultraviolet aging and freeze-thaw erosion, making it difficult to form a long-term reliable insulation and protection system.

[0004] Temperature stress control in dam structures primarily relies on temperature-controlled water flow and surface insulation, which are passive temperature control methods. These methods can only slow down the rate of temperature change and cannot fundamentally release existing temperature stress. Some technologies using a "short transverse joint + steel mesh + waterstop" approach can largely eliminate transverse cracks on the upstream dam face, but cannot completely solve the problem of horizontal cracks caused by vertical temperature stress. Some projects also use horizontal joints or expansion joints, but these suffer from problems such as unreasonable joint depth design, inconsistent waterstop systems, and inadequate reinforcement. These issues prevent them from forming a synergistic crack prevention mechanism with the insulation system, making it difficult to meet the long-term safe operation requirements of concrete gravity dams in high-altitude and cold regions.

[0005] Therefore, developing an anti-cracking structure for the upstream face of a cold-region concrete gravity dam that integrates long-term thermal insulation, frost and impact resistance, stress release, reliable seepage prevention, and overall reinforcement is of great engineering value and technical significance for improving the crack resistance and service life of dams in cold regions. Utility Model Content

[0006] The purpose of this application is to provide a crack-resistant structure for the upstream face of a concrete gravity dam in cold regions, so as to solve or alleviate the problems existing in the prior art.

[0007] To achieve the above objectives, this application provides the following technical solution: This application provides a crack-prevention structure for the upstream face of a cold-region concrete gravity dam, including a GRC composite extruded polystyrene board installed on the upstream face, a horizontal pre-reserved joint installed at a location with high vertical stress in the dam body, an asphalt resin isolation layer installed within the horizontal pre-reserved joint, and a water-stopping system installed at the horizontal pre-reserved joint; the water-stopping system is integrated with the water-stopping system of the transverse joint of the dam body to form a double continuous seepage prevention system; the depth of the horizontal pre-reserved joint is the distance from the upstream face of the dam to the second water-stopping system of the transverse joint of the dam; and a crack-limiting steel mesh is provided around the horizontal pre-reserved joint and behind the water-stopping system.

[0008] Furthermore, the GRC composite extruded board is composed of a 10±2mm thick GRC protective layer and a 100±2mm thick XPS extruded board layer, and is an integrated board prefabricated in the factory; the XPS extruded board layer is in close contact with the upstream dam surface, and the GRC protective layer faces outward.

[0009] Furthermore, the pre-crack limiting steel mesh set around the horizontal reserved joint is 90mm to 120mm away from the dam surface and is interrupted at the horizontal reserved joint; the crack limiting steel mesh set behind the water-stopping system is 90mm to 120mm away from the rear end of the water-stopping system and its vertical height is 1200mm to 1500mm; the crack limiting steel mesh uses HRB400 grade φ16 steel bars with a spacing of 200mm to 220mm; preferably, the spacing of the steel bars in the crack limiting steel mesh is 200mm.

[0010] Furthermore, the water-stopping system at the horizontal reserved joint includes a second horizontal water-stop plate disposed at the end of the horizontal reserved joint and a first horizontal water-stop plate disposed in front of the second horizontal water-stop plate; the second horizontal water-stop plate is integrated with the second water-stop of the dam's transverse joint. The first horizontal water-stop plate is flush with the first water-stop of the dam's transverse joint, that is, the distance between the first horizontal water-stop plate and the dam surface is equal to the distance between the first water-stop of the dam's transverse joint and the dam surface, thereby facilitating the integration of the first horizontal water-stop plate with the first water-stop of the dam's transverse joint. Specifically, the first horizontal water-stop plate is disposed 600mm to 1000mm in front of the second horizontal water-stop plate, and the depth of the horizontal reserved joint is 1000mm to 1600mm.

[0011] Specifically, the first horizontal waterstop is an embedded rubber waterstop, and the second horizontal waterstop is an embedded copper waterstop.

[0012] Furthermore, an asphalt-impregnated hemp rope is provided at the end of the horizontal reserved joint, and the asphalt-impregnated hemp rope is placed inside the copper lug of the second horizontal waterstop.

[0013] The construction method for the crack prevention structure on the upstream face of a cold-region concrete gravity dam, as described in this application, includes the following steps: (1) The elevation of the top surface of the first layer before the horizontal reserved joint is poured into the dam concrete; (2) Install asphalt hemp rope and the second horizontal waterstop, and connect the second horizontal waterstop to the transverse joint copper waterstop; (3) Install the first horizontal waterstop and connect it to the first waterstop of the transverse joint of the dam; (4) Install and sew the reinforcing mesh; (5) Install the portion of the pre-splitting steel mesh below the horizontal reserved joint near the upstream dam face, and disconnect the pre-splitting steel mesh at the reserved joint; (6) The dam body concrete is poured to the design elevation of the horizontal reserved joint; (7) Form a horizontal reserved joint, the joint depth of which is the distance from the dam surface to the second water stop of the dam's transverse joint, and the joint surface is coated with asphalt grease; (8) Install the portion of the pre-splitting steel mesh above the horizontal reserved joint near the upstream dam face, and disconnect the pre-splitting steel mesh at the reserved joint; (9) Pouring concrete for the upper dam body; (10) Anchor GRC composite extruded polystyrene board on the upstream dam face to complete the construction of the overall crack prevention structure.

[0014] The technical solution of this application has the following beneficial effects: This application achieves highly efficient crack prevention and seepage control on the upstream face of a gravity dam in cold regions through the synergistic effect of thermal insulation, protection, stress release, and multiple water-stopping and crack-limiting structures. Specifically, the GRC composite extruded polystyrene board possesses erosion resistance, freeze-thaw resistance, and ice pull-out resistance, while also providing highly efficient thermal insulation. This significantly reduces freeze-thaw erosion of the dam face concrete, improves the durability of the insulation layer and the dam structure, greatly reduces the temperature difference between the inside and outside of the dam face, and significantly reduces thermal shrinkage stress, thus inhibiting crack formation at its source. The horizontal pre-reserved joints extend to the second water-stopping layer of the dam's transverse joints, effectively releasing internal temperature stress and preventing stress concentration that could lead to deep cracking. The water-stopping system forms a multi-layered seepage prevention system and is continuously connected to the transverse joint water-stopping layer, ensuring high reliability in seepage prevention. The crack-limiting steel mesh enhances the integrity and tensile strength of the joint area and the dam face concrete, preventing abnormal deformation of the joint surface. The synergistic effect of the above-mentioned thermal insulation structure and joint construction results in a significant crack prevention effect, greatly improving the crack resistance and long-term service life of the upstream face of a gravity dam in cold regions. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein: Figure 1 This is a structural schematic diagram of an embodiment of the present utility model.

[0016] Explanation of reference numerals in the attached figures: 1-Upstream dam face, 2-XPS extruded polystyrene board layer, 3-GRC protective layer, 4-Pre-crack limiting steel mesh, 5-Jointed steel mesh, 6-Horizontal reserved joint, 7-Horizontal construction joint, 8-First horizontal waterstop, 9-Second horizontal waterstop, 10-Asphalt hemp rope. Detailed Implementation

[0017] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment.

[0018] In the following description, the terms "first / second" are used merely to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first / second" may be interchanged in a specific order or sequence where permitted, so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing embodiments of this disclosure only and is not intended to limit this disclosure.

[0020] In the description of this application, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and do not require this application to be constructed and operated in a specific orientation, and therefore should not be construed as limiting this application. The terms "connected," "linked," and "set up" used in this application should be interpreted broadly.

[0021] like Figure 1 As shown, this application provides a crack prevention structure for the upstream face of a cold-region concrete gravity dam, including a GRC composite extruded polystyrene board installed on the upstream face 1, a horizontal reserved joint 6 installed at a location with high vertical stress in the dam body, an asphalt resin isolation layer installed in the horizontal reserved joint 6, and a water-stopping system installed at the horizontal reserved joint 6. The water-stopping system at the horizontal reserved joint 6 includes a second horizontal water-stop plate 9 set at the end of the horizontal reserved joint 6 and a first horizontal water-stop plate 8 set in front of the second horizontal water-stop plate 9; the water-stopping system is integrated with the water-stopping system of the transverse joint of the dam body to form a double continuous seepage prevention system; the depth of the horizontal reserved joint 6 is the distance from the upstream dam face 1 to the second water-stopping system of the transverse joint of the dam; crack-limiting steel mesh is provided around the horizontal reserved joint 6 and behind the water-stopping system; The GRC composite extruded polystyrene board is composed of a 10±2mm thick GRC protective layer 3 and a 100±2mm thick XPS extruded polystyrene board layer 2. It is an integrated board prefabricated in the factory, and the two together constitute the dam surface insulation and protection system. The XPS extruded polystyrene board layer 2 is closely attached to the upstream dam surface 1, and the GRC protective layer 3 faces outward. The XPS extruded polystyrene board layer 2 has excellent thermal insulation performance, which can significantly reduce the temperature difference between the dam concrete and the external environment and reduce the tensile stress caused by temperature drop and shrinkage. The GRC protective layer 3 has high strength, high frost resistance and erosion resistance, which can resist the erosion of reservoir water, ice and freeze-thaw cycles, prevent the insulation layer from being damaged and falling off, and ensure the long-term stability of the insulation effect.

[0022] This application achieves multiple synergistic crack prevention effects by setting an insulation structure on the outer side of the upstream dam face 1, and simultaneously setting a horizontal reserved joint 6 and matching water-stopping and steel reinforcement structure inside the dam body, thereby reducing the temperature difference between the inside and outside of the dam body, releasing temperature stress, blocking crack development, and improving seepage prevention capabilities.

[0023] The horizontal reserved joint 6 is located at a point of high vertical tensile stress in the dam body. For higher dams that require several years to pour and construct to the top, i.e., dams with multiple winter-endurance layers, the point of high vertical tensile stress refers to the area near the winter-endurance layer of the upstream dam face 1. For lower dams that can be poured and constructed to the top in the same year, i.e., dams without winter-endurance layers, the point of high vertical tensile stress refers to a certain range along the dam height near the middle. The depth of the horizontal reserved joint 6 is 1000mm to 1600mm, which is equivalent to the distance between the second waterstop upstream of the dam's transverse joint and the upstream dam face 1, i.e., extending inward from the upstream dam face 1 to the position of the second waterstop of the transverse joint. The surface of the horizontal reserved joint 6 is evenly coated with asphalt resin to form an asphalt resin isolation layer, thereby reducing the adhesion force of the joint surface and ensuring that the reserved joint can effectively release the internal temperature stress of the dam body, avoiding stress concentration that could cause deep cracks.

[0024] The first horizontal waterstop 8 is installed 1400mm to 600mm from the upstream dam face. The first horizontal waterstop 8 is reliably connected to the first waterstop of the transverse joint of the dam body, forming the first line of seepage prevention. The second horizontal waterstop 9 is installed 600mm to 1000mm behind the first horizontal waterstop 8, that is, at the end of the horizontal reserved joint 6. The second horizontal waterstop 9 is reliably connected to the second waterstop of the transverse joint of the dam body, forming the second line of seepage prevention. The two waterstops and the asphalt resin isolation layer together constitute a multi-layer seepage prevention system, effectively blocking the reservoir water from seeping into the interior of the dam body along the reserved joint.

[0025] Specifically, the material of the first horizontal waterstop 8 is the same as that of the first waterstop in the transverse joint of the dam body, and the material of the second horizontal waterstop 9 is the same as that of the second waterstop in the transverse joint of the dam body. For example, if the first waterstop in the transverse joint of the dam body is a rubber waterstop and the second waterstop is a copper waterstop, then the first horizontal waterstop 8 is a centrally embedded rubber waterstop and the second horizontal waterstop 9 is a copper waterstop, preferably a centrally embedded copper waterstop.

[0026] For ease of description, the crack-limiting steel mesh surrounding the horizontal reserved joint 6 is referred to as the front crack-limiting steel mesh 4, and the crack-limiting steel mesh located behind the water-stopping system is referred to as the parallel-joint steel mesh 5. The front crack-limiting steel mesh 4 is 90mm to 120mm from the dam surface, preferably 100mm from the dam surface, and is interrupted at the horizontal reserved joint 6 to avoid the steel mesh forming a rigid constraint on the reserved joint, which would affect the temperature stress release effect. The parallel-joint steel mesh 5 is 90mm to 120mm from the rear end of the water-stopping system, and its total vertical height is 1200mm to 1500mm; preferably, the parallel-joint steel mesh 5 is 100mm from the rear end of the water-stopping system, and its total vertical height is 1200mm, arranged 600mm above and below the horizontal reserved joint 6 as the center, to improve the tensile strength and integrity of the concrete in the joint area and limit the deformation and cracking of the joint surface. The crack-limiting steel mesh uses HRB400 grade φ16 steel bars with a spacing of 200mm to 220mm; preferably, the spacing of the steel bars in the crack-limiting steel mesh is 200mm.

[0027] Furthermore, an asphalt hemp rope 10 with a diameter of 15mm to 20mm is provided at the end of the horizontal reserved joint 6, and the asphalt hemp rope 10 is provided inside the copper nose of the second horizontal waterstop 9; preferably, the diameter of the asphalt hemp rope 10 is 15mm.

[0028] During construction, the dam concrete is first poured in layers to the elevation of the top surface of the layer before the horizontal reserved joint 6; the first horizontal waterstop 8, the second horizontal waterstop 9, and the asphalt hemp rope 10 are installed in sequence and reliably connected to the waterstop of the horizontal joint of the dam; the steel mesh 5 is installed and joined together; the portion of the pre-splitting steel mesh 4 below the horizontal reserved joint 6 near the upstream dam face 1 is installed, and the pre-splitting steel mesh 4 is broken at the reserved joint; the dam concrete is poured to the design elevation of the horizontal reserved joint 6; the horizontal reserved joint 6 is formed according to the design position, and the joint surface is coated with asphalt grease. The initial joint width of the horizontal reserved joint 6 is the thickness of the asphalt grease coating, and no additional opening is required; the portion of the pre-splitting steel mesh 4 above the horizontal reserved joint 6 near the upstream dam face 1 is installed, and the pre-splitting steel mesh 4 is broken at the reserved joint; the upper part of the dam concrete is poured to form a complete dam structure; Figure 1 The horizontal reserved joint 6 and the horizontal construction joint 7 are schematically marked. Finally, GRC composite extruded polystyrene board is installed on the upstream dam face 1 to complete the thermal insulation and protection construction.

[0029] Engineering monitoring results show that after adopting this application, the temperature difference between the inside and outside of the dam surface is reduced by more than 60%, the temperature drop shrinkage stress is significantly reduced, the horizontal reserved joints can effectively release the temperature stress of the dam body, no surface cracks or leakage occur in the dam body, freeze-thaw erosion is effectively controlled, and the crack prevention and durability effects are significantly better than traditional heat preservation and crack prevention measures.

[0030] Verification Example To further illustrate the rationality of the horizontal reserved joint in this application, the following will use a white stone concrete gravity dam as an example to verify it using finite element nonlinear simulation.

[0031] The Baishi Concrete Gravity Dam is located in Beipiao City, Liaoning Province. It has a maximum height of 50.3 meters and a concrete volume of 575,000 cubic meters. 3 The main dam construction began in September 1996 and was completed in 2000.

[0032] In this verification example, the GRC composite extruded polystyrene board is composed of a 10mm thick GRC protective layer and a 100mm thick XPS extruded polystyrene board layer; the depth of the horizontal reserved joint is 1000mm; the first horizontal waterstop is set at 400mm from the upstream dam surface, and the second horizontal waterstop is set at the end of the horizontal reserved joint; the front-limiting crack reinforcement mesh uses HRB400 grade φ16 steel bars with a spacing of 200mm; the front-limiting crack reinforcement mesh is 100mm from the dam surface and is broken at the joint; the parallel joint reinforcement mesh uses HRB400 grade φ16 steel bars with a spacing of 200mm, is 100mm from the rear end of the waterstop system, and its total height is 1200mm.

[0033] A horizontal pre-reserved joint was selected on the upstream face of a typical dam section, and finite element nonlinear simulation analysis was performed to analyze the feasibility of setting the horizontal pre-reserved joint, stress distribution, stability of the pre-reserved joint, role of reinforcement, and impact on the interlayer anti-sliding stability of the dam body. A joint-coated model was used to simulate the pre-reserved joint in the dam body, and an energy failure criterion was established for the crack tip. Softening damage was introduced into the fracture mechanics model to more accurately describe the constitutive behavior of concrete near the crack tip. A fracture mechanics crack zone model was introduced into the strain softening model to overcome the difficulty of strong mesh sensitivity in strain softening mathematical calculations. Calculation results show that the principal tensile stress at the location with the horizontal pre-reserved joint on the upstream face of the dam section decreased from 2.24 MPa without the pre-reserved joint to 0.98 MPa; the upstream pre-reserved joint extended inward by 0.27 m to reach stability. The interlayer anti-sliding stability of the section with the horizontal pre-reserved joint in the dam section was verified. Using the shear resistance formula of mechanics of materials, the interlayer anti-sliding stability safety factor is much greater than the allowable safety factor, and the anti-sliding stability meets the requirements. The research results on the calculation of horizontal reserved joints in Baishi concrete gravity dams can be found in the reference "Research and Application of Reserved Joints in Baishi Roller-Compacted Concrete Gravity Dams" (Wang Chengshan, Han Guocheng, Lü Hexiang. Research and Application of Reserved Joints in Baishi Roller-Compacted Concrete Gravity Dams [J]. Journal of Hydraulic Engineering, 2003, 34(9):107-111.).

[0034] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A crack prevention structure for the upstream face of a concrete gravity dam in cold regions, characterized by: It includes a GRC composite extruded polystyrene board set on the upstream dam face (1), a horizontal reserved joint (6) set on the part of the dam body with large vertical stress, an asphalt resin isolation layer set in the horizontal reserved joint (6), and a water-stopping system set at the horizontal reserved joint (6); the water-stopping system and the water-stopping system of the dam body are integrated to form a double continuous seepage prevention system; the depth of the horizontal reserved joint (6) is the distance from the upstream dam face (1) to the second water-stopping system of the dam's horizontal joint; and a crack-limiting steel mesh is provided around the horizontal reserved joint (6) and behind the water-stopping system.

2. The anti-crack structure for the upstream face of a cold-region concrete gravity dam according to claim 1, characterized in that: The GRC composite extruded board is composed of a 10±2mm thick GRC protective layer (3) and a 100±2mm thick XPS extruded board layer (2); the XPS extruded board layer (2) is in close contact with the upstream dam surface (1), and the GRC protective layer (3) faces outward.

3. The anti-crack structure for the upstream face of a cold-region concrete gravity dam according to claim 1, characterized in that: The depth of the horizontal reserved gap (6) is 1000mm to 1600mm.

4. The anti-crack structure for the upstream face of a cold-region concrete gravity dam according to claim 1, characterized in that: The crack-limiting steel mesh set around the horizontal reserved joint (6) is 90mm to 120mm away from the dam surface and is broken at the horizontal reserved joint (6); the crack-limiting steel mesh set behind the water-stopping system is 90mm to 120mm away from the rear end of the water-stopping system and its vertical height is 1200mm to 1500mm.

5. The anti-crack structure for the upstream face of a cold-region concrete gravity dam according to claim 1, characterized in that: The crack-limiting steel mesh uses HRB400 grade φ16 steel bars with a spacing of 200mm to 220mm.

6. The anti-crack structure for the upstream face of a cold-region concrete gravity dam according to claim 1, characterized in that: The water-stopping system at the horizontal reserved joint (6) includes a second horizontal water-stopping plate (9) set at the end of the horizontal reserved joint (6) and a first horizontal water-stopping plate (8) set in front of the second horizontal water-stopping plate (9); the first horizontal water-stopping plate (8) is flush with the position of the first water-stopping layer of the dam's transverse joint; the first horizontal water-stopping plate (8) is integrated with the first water-stopping layer of the dam's transverse joint, and the second horizontal water-stopping plate (9) is integrated with the second water-stopping layer of the dam's transverse joint.

7. The anti-crack structure for the upstream face of a cold-region concrete gravity dam according to claim 6, characterized in that: The first horizontal waterstop (8) is positioned 600mm to 1000mm in front of the second horizontal waterstop (9).

8. The anti-crack structure for the upstream face of a cold-region concrete gravity dam according to claim 6, characterized in that: The first horizontal waterstop (8) is a centrally embedded rubber waterstop, and the second horizontal waterstop (9) is a centrally embedded copper waterstop.

9. The anti-crack structure for the upstream face of a cold-region concrete gravity dam according to claim 6, characterized in that: The end of the horizontal reserved joint (6) is provided with an asphalt hemp rope (10) with a diameter of 15mm to 20mm, and the asphalt hemp rope (10) is set inside the copper nose of the second horizontal waterstop (9).

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