Rock-fill dam concrete panel joint structure and construction method thereof

Abstract

The invention provides a rock-fill dam concrete panel joint structure and a construction method thereof, and belongs to the technical field of water conservancy and hydropower engineering. The concrete panel joint structure comprises a hydraulic engineering ECC material layer, an induction joint and an in-joint sealing layer. Wherein the hydraulic engineering ECC material layer is arranged in a joint of the concrete panel; the inducing joint is arranged in a mortar cushion layer and an emulsified asphalt layer below the middle of the joint of the concrete panel; and sealing the inducing joint by adopting a sealing material to form an in-joint sealing layer. The stress of the concrete panel is induced to the designated position by arranging the inducing joint, the structural joint is arranged at the position, and meanwhile, the hydraulic engineering ECC material is adopted as the joint filling material, so that the cracking risk of the concrete panel is greatly reduced, and the anti-seepage reliability of the joint structure is improved. Moreover, the concrete panel joint structure is suitable for continuous pouring construction of a rock-fill dam panel, is also suitable for panel repairing construction, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy and hydropower engineering, and particularly relates to a joint structure of a concrete face slab of a rockfill dam and a construction method thereof. Background Art

[0002] Concrete face rockfill dams have occupied an increasingly large proportion in hydropower construction due to their advantages such as low project cost, simple construction, and strong adaptability to topography and geology, and have become one of the most popular dam types today, with wide applications.

[0003] The concrete face slab is located on the upstream surface of the rockfill dam body and plays a role in seepage prevention. The concrete face slab is in a three-dimensional complex stress state around the two abutments of the dam, and most of it is in the tensile zone, prone to tensile failure, while the middle part of the face slab is mostly in the compression zone, prone to extrusion failure. In order to avoid cracking and extrusion failure of the concrete face slab and at the same time adapt to the deformation of the rockfill, construction by dividing joints and blocks is usually adopted, that is, a vertical permanent joint is set every about 15 m to 20 m along the dam axis direction of the entire concrete face slab, and a horizontal joint is set along the elevation, so as to form independent concrete blocks. The joints around each concrete block are very important for the upstream impervious body of the hydropower station. That is to say, the original intention of setting structural joints is to cope with the cracking and extrusion failure caused by uneven deformation and large stress of the concrete face slab of the rockfill dam in the direction perpendicular to the dam axis. Structural joints are set in the areas with large stress to release the stress of the face slab, thereby reducing the risk of cracking of the concrete face slab. However, due to the uncertainty of the deformation and stress of the concrete face slab related to the characteristics of the rockfill body, filling method, environmental factors, etc., it is very difficult to exactly set the structural joints at the positions where the deformation and stress of the concrete face slab are the largest during the design stage. Therefore, from the perspective of engineering practice, simply setting structural joints and water stops cannot completely eliminate the phenomenon of cracking and leakage of the concrete face slab. Even if fiber concrete materials are used to improve the anti-seepage performance of the joints, cracking and leakage problems will still occur in other areas of the face slab.

[0004] At present, multiple water stops are used for combined anti-seepage on the surface layer of the concrete face slab joints. The specific construction process includes: foundation trench cleaning, primer coating, plastic filler embedding, composite cover plate pasting, water stop installation and fixation, edge sealing agent edge sealing and other treatment processes. Even so, the joints between concrete blocks still constitute obvious weak surfaces, and leakage still occurs, mainly because the filler between the joints itself does not have anti-seepage function and is a weak link in the anti-seepage system of the rockfill dam.

[0005] Hydraulic ECC (Engineered Cementitious Composites) material is a high-performance fiber-reinforced cementitious composite material. Toughness-increasing fibers are incorporated during the mixing process. Through mix proportion adjustment, it can have the characteristics of ultra-high ductility and toughness, and high compressive strength. At the same time, even if the hydraulic ECC material cracks, the cracks are dispersed and fine, with the width of a single crack being 20 - 80 μm, so that the hydraulic ECC material itself will not leak. At the same time, it is a cementitious material like concrete and has good bonding performance with concrete. By improving the vibration method, it can ensure that there is no obvious weak surface at the joint, and it is very suitable for joint construction. Due to the excessive fluidity of the cementitious composite material and the increase in the difficulty of vibration caused by the incorporation of fibers, currently, it cannot be directly applied to the facing slab of a rockfill dam with slope construction requirements. Summary of the Invention

[0006] Aiming at the problem that during the design stage, the structural joint is difficult to be exactly at the position where the deformation and stress of the concrete slab are the largest, resulting in cracking and leakage of the concrete slab, the present invention provides a joint structure for the concrete slab of a rockfill dam and its construction method. By setting the form of induced joints, the stress of the concrete slab is induced to a specified position, and a structural joint is set at this position. At the same time, hydraulic ECC material is used as the joint filling material, and the filling material itself has strong anti-seepage characteristics and the fluidity meets the construction requirements. The joint structure of the present invention can greatly reduce the leakage problem of the concrete slab of the rockfill dam. The concrete slab joint structure is applicable to the continuous pouring construction of the facing slab of the rockfill dam and is also applicable to the repair construction of the slab, with broad application prospects.

[0007] To achieve the above object, the specific technical solutions of the present invention are as follows:

[0008] A joint structure for the concrete slab of a rockfill dam, comprising: a hydraulic ECC material layer, induced joints, and an in-seam sealing layer; wherein, the hydraulic ECC material layer is arranged in the joint of the concrete slab; the induced joints are arranged in the mortar cushion layer and the emulsified asphalt layer below the middle of the joint of the concrete slab; a sealing material is used to seal the induced joints to form an in-seam sealing layer.

[0009] The joint structure of the concrete face slab of the rockfill dam of the present invention includes: a hydraulic ECC material layer, induced joints, and a seal layer inside the joints. Among them, the hydraulic ECC material used in the hydraulic ECC material layer is designed with a low slump mix ratio, and its fluidity meets the requirements of face slab construction. During construction, it can ensure that the hydraulic ECC material and the concrete material penetrate each other, so that no structural joints are formed at the interface; a wide joint is cut in the mortar cushion layer and the emulsified asphalt layer at the middle position of the joint to form an induced joint. The induced joint directly connects the upper face slab and the lower rockfill body, so as to guide all the large stress areas of the upper face slab caused by the deformation of the lower rockfill body to the hydraulic ECC material section, and a sealing material is used to seal the induced joint to form a seal layer inside the joint to prevent leakage of the induced joint during deformation.

[0010] Further, the sealing material includes but is not limited to cationic emulsified asphalt, foam material, or rubber material.

[0011] Further, the raw materials of the hydraulic ECC material used in the hydraulic ECC material layer include: 15wt% - 22wt% of cement, 0.5wt% - 1.5wt% of polyethylene (PE) fiber, 39wt% - 48wt% of fine sand, 20wt% - 25wt% of fly ash, 0.3% - 1.0wt% of water reducing agent, and 0 - 2wt% of expansive agent.

[0012] Furthermore, the raw materials of the hydraulic ECC material used in the hydraulic ECC material layer are: 17wt% of cement, 1wt% of polyethylene fiber, 45wt% of fine sand, 22wt% of fly ash, 0.4wt% of water reducing agent, and 0.6wt% of expansive agent, and the rest is water.

[0013] Furthermore, the slump of the hydraulic ECC material is less than 100 mm.

[0014] Furthermore, the vibration of the hydraulic ECC material is carried out by an inserted high-frequency vibration rod with a frequency of 100 - 200Hz. The vibration rod is inserted 10 - 20 cm into the lower layer, and the single vibration time is 20 - 40 s to ensure the effective fusion of the hydraulic ECC material and the concrete.

[0015] Further, a copper sheet water stop is arranged at the interface between the hydraulic ECC material layer and the conventional concrete. The copper water stop sheet is connected by double-sided lap welding, and the lap length is not less than 20 mm.

[0016] Further, the width of the induced joint is 20 - 40 cm.

[0017] The present invention also provides a construction method for the joint structure of the concrete face slab of the rockfill dam, including the following steps:

[0018] (1)Reserved induced joints: Reasonably design the positions of the joint structures of the concrete slabs of the rockfill dam, cut the mortar cushion layer and the emulsified asphalt layer at the joint positions to form induced joints, and make the joint surfaces flat and perpendicular to the slope direction;

[0019] (2)Sealing of induced joints: Clean the induced joints, and use sealing materials to seal the induced joints to form a sealing layer inside the joints. The sealing position is flush with the bottom of the adjacent concrete slabs;

[0020] (3)Roughening treatment of the concrete ends: Perform chiseling treatment on the surface of the adjacent cast conventional concrete, chisel off the surface floating mortar to expose the internal aggregate. The roughness of the treated surface is greater than 2 mm, and then rinse it clean;

[0021] (4)Pouring and vibrating of hydraulic ECC material: Continuously construct the hydraulic ECC material in a full-section paving manner to eliminate the construction joint surfaces caused by long intervals; During the pouring process, use high-frequency vibrating rods for vibration. The vibrating rods are inserted 10 - 20 cm into the lower layer, and the single vibration time is 20 - 40 s to ensure the effective fusion of the hydraulic ECC material and the adjacent concrete;

[0022] (5)Heat preservation and curing of the joint structure: Conduct curing and heat preservation after pouring.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] By setting the form of induced joints, the present invention induces the stress of the concrete slabs to the designated positions, sets structural joints at these positions, and at the same time uses hydraulic ECC material as the joint filling material, which greatly reduces the risk of cracking of the concrete slabs and improves the anti-seepage reliability of the joint structure. Moreover, the joint structure of the concrete slabs is applicable to the continuous pouring construction of the rockfill dam slabs and is also applicable to the slab repair construction, having a wide application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a joint structure of a concrete slab of a rockfill dam according to the present invention; In the figure: 1. Hydraulic ECC material layer; 2. Sealing layer inside the joint; 3. Induced joint; 4. Emulsified asphalt layer; 5. Mortar cushion layer; 6. Conventional concrete slab. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0027] The present invention provides a joint structure for the concrete face slab of a rockfill dam. Below the concrete face slab are successively a mortar cushion layer, an emulsified asphalt layer, and a rockfill body. The joint structure includes: a hydraulic ECC material layer 1, a closed layer 2 inside the joint, and an induced joint 3. Among them, the hydraulic ECC material layer 1 is arranged in the joint of the concrete face slab; the induced joint 3 is arranged in the mortar cushion layer 5 and the emulsified asphalt layer 4 below the middle of the joint of the concrete face slab; the induced joint 3 is sealed with a sealing material to form the closed layer 2 inside the joint. The hydraulic ECC material used in the hydraulic ECC material layer 1 is designed with a low slump mix ratio, and its fluidity meets the requirements of face slab construction. A wide joint is cut in the mortar cushion layer 5 and the emulsified asphalt layer 4 at the middle position of the joint to form the induced joint 3, so as to guide the microcracks to only appear in the hydraulic ECC material section, and the induced joint 3 is sealed with cationic emulsified asphalt, foam material or rubber material to form the closed layer 2 inside the joint to prevent leakage of the induced joint during deformation. The surface of the pouring layer is vibrated by an inserted high-frequency vibrator to ensure that the hydraulic ECC material and the concrete material penetrate each other, so that no structural joint is formed at the interface.

[0028] In the following specific embodiments, the cement is commercially available P·O 42.5 ordinary Portland cement; the polyethylene fiber has a diameter of 40 μm, a length of 12 mm, a breaking strength > 1300 MPa, and an elastic modulus > 30 GPa; the fine sand is quartz sand with a diameter less than 1.25 mm; the fly ash meets Class F Grade I fly ash in the Technical Specification for Use of Fly Ash in Hydraulic Concrete (DL / T 5055 - 2007); the water reducing agent is a commercially available high-performance polycarboxylate water reducing agent; the expansion agent is a commercially available sulfoaluminate-based concrete expansion agent.

[0029] Example 1

[0030] A joint structure for a face slab suitable for continuous pouring, and the mix ratio of the hydraulic ECC material used in its hydraulic ECC material layer is: cement 17wt%, polyethylene fiber 1wt%, fine sand 45wt%, fly ash 22wt%, water reducing agent 0.4wt%, and expansion agent 0.6wt%, and the rest is water.

[0031] The specific construction method is as follows:

[0032] S1. Reserve the induced joint

[0033] Design the position of a reasonable joint structure, and use a cutting machine to cut the mortar cushion layer and the asphalt layer at the joint position to form an induced joint. The cutting width is 30 cm, and ensure that the joint surface is flat and perpendicular to the slope direction.

[0034] S2. Seal the induced joint

[0035] Clean the induced joints, and then seal the induced joints with cationic emulsified asphalt. The filling position of the cationic emulsified asphalt is flush with the bottom of the adjacent concrete slab.

[0036] S3. Roughening treatment of the concrete end

[0037] Roughen the surface of the cast conventional concrete, chisel off the surface floating slurry to expose the internal aggregate. The roughness of the treated surface is greater than 2 mm, and then rinse it with clean water.

[0038] S4. Pouring and vibrating of hydraulic ECC material

[0039] The hydraulic ECC material is continuously constructed in a full-section paving method without interruption to eliminate the construction joints caused by long intervals. During the pouring process, a high-frequency vibrating rod is used for vibration. The vibrating rod is inserted into the lower layer by 10 - 20 cm, and the single vibration time is 20 - 40 s to ensure the effective fusion of the hydraulic ECC material and the concrete.

[0040] S5. Heat preservation and curing of the joint structure

[0041] Conduct curing and heat preservation after pouring.

[0042] To verify the implementation effect of the joint structure, in addition to this embodiment (ET1), a conventional concrete slab (ET2) was also poured as a control group. The conventional concrete slab was poured and constructed in accordance with the Construction Specifications for Concrete Faced Rockfill Dams (SL 49 - 2015). Core samples of the slab at the joint were selected on-site for impermeability detection, and the detection results are shown in Table 1.

[0043] Table 1: Impermeability test results of the slab at the joint

[0044]

[0045] As can be seen from Table 1, after construction, the permeability coefficients of the conventional concrete slab (ET2) and the concrete slab of this embodiment (ET1) are close, both in the -7 order of magnitude, indicating that their impermeability is close. However, with the extension of the service life, the permeability coefficient of the conventional concrete slab has increased by two orders of magnitude, while the increase in the permeability coefficient of the concrete slab of this embodiment is not significant, indicating that the joint structure of the concrete slab in this embodiment has good impermeability. In addition, the inventor's research found that if the induced joints are not pre-sealed with a sealing material but directly filled with hydraulic ECC material, when the hydraulic ECC material cures and completely seals the induced joints, the effect of guiding all the large stress areas of the upper slab caused by the deformation of the lower rockfill body to the structural joints cannot be achieved. If the induced joints only exist in the mortar cushion layer and do not penetrate into the emulsified asphalt layer, the same effect of guiding all the large stress areas of the upper slab caused by the deformation of the lower rockfill body to the structural joints cannot be achieved.

[0046] Example 2

[0047] A panel joint structure suitable for the repair of the face slab of a rockfill dam. The mix ratio of the hydraulic ECC material used in the hydraulic ECC material layer is as follows: cement 17wt%, polyethylene fiber 1wt%, fine sand 45wt%, fly ash 22wt%, water reducing agent 0.4wt%, and expansive agent 0.6wt%, with the rest being water.

[0048] The specific construction method is as follows:

[0049] S1. Cleaning and construction preparation of the panel joint

[0050] Demolish the joint structure that needs to be repaired, clean the working surface, and complete the installation of construction formwork and other work.

[0051] To ensure the sealing of the joint end, first set a copper sheet waterstop at the end of the adjacent concrete panel, and the waterstop penetrates into the mortar cushion layer.

[0052] S2. Leveling construction of the mortar cushion layer

[0053] Spread M30 mortar on the original mortar cushion layer, compact the mortar cushion layer, and level it to the plane required by the mortar cushion layer.

[0054] S3. Reserved induced joint

[0055] Use a cutting machine to cut the mortar cushion layer and the emulsified asphalt layer at the joint position. The cutting width is 30 cm, and ensure that the joint surface is flat and perpendicular to the slope direction.

[0056] S4. Emulsified asphalt construction

[0057] Adopt the "two oils and two sands" process, that is, alternately spray modified emulsified asphalt and sprinkle sand twice on the surface of the mortar cushion layer. During the emulsified asphalt construction, cover the mortar cushion layer near the induced joint with a plastic film to prevent the emulsified asphalt from being sprayed on this area.

[0058] S5. Filling of the induced joint

[0059] First, clean the induced joint, and then use cationic emulsified asphalt to seal the induced joint. The filling position of the cationic emulsified asphalt is flush with the bottom of the adjacent concrete panel.

[0060] S6. Pouring and vibrating of the hydraulic ECC material

[0061] The hydraulic ECC material is continuously constructed in a full-section paving manner to eliminate the construction joint surface caused by long intervals; during the pouring process, use a high-frequency vibrating rod to vibrate. The vibrating rod is inserted into the lower layer by 10 - 20 cm, and the single vibrating time is 20 - 40 s to ensure the effective fusion of the hydraulic ECC material and the concrete.

[0062] S7. Curing and heat preservation of the joint structure

[0063] Curing and heat preservation shall be carried out after pouring is completed.

[0064] To sum up, by setting the form of induced joints, the stress of the concrete slab is induced to the designated position, a structural joint is set at this position, and at the same time, the hydraulic ECC material is used as the joint filling material, which greatly reduces the risk of cracking of the concrete slab and improves the anti-seepage reliability of the joint structure.

[0065] The above specific embodiments have described the implementation of the present invention in detail. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple variations all belong to the protection scope of the present invention.

Claims

1. A rockfill dam concrete panel joint structure, characterized in that: include: A hydraulic ECC material layer, an induced joint and an inner joint sealing layer; wherein the hydraulic ECC material layer is arranged in the joint of the concrete panel; The induced joint is arranged in the mortar cushion layer and the emulsified asphalt layer below the middle of the concrete panel joint; the induced joint is sealed with a sealing material to form a sealing layer in the joint.

2. A rockfill dam concrete panel joint structure according to claim 1, characterized in that: The sealing material includes but is not limited to cationic emulsified asphalt, foam material or rubber material.

3. The rockfill dam concrete panel joint structure according to claim 1, characterized in that: The raw materials of the hydraulic ECC material used in the hydraulic ECC material layer include: 15wt%~22wt% cement, 0.5wt%~1.5wt% polyethylene fiber, 39wt%~48wt% fine sand, 20wt%~25wt% fly ash, 0.3%~1.0wt% water reducer and 0~2wt% expansion agent.

4. A rockfill dam concrete panel joint structure according to claim 3, characterized in that: The raw materials of the hydraulic ECC material used in the hydraulic ECC material layer are: 17wt% cement, 1wt% polyethylene fiber, 45wt% fine sand, 22wt% fly ash, 0.4wt% water reducer and 0.6wt% expansion agent, and the rest is water.

5. The rockfill dam concrete panel joint structure according to claim 3, characterized in that: The slump of the hydraulic ECC material is less than 100 mm.

6. The rockfill dam concrete panel joint structure according to claim 3, characterized in that: The hydraulic ECC material is vibrated using an inserted high-frequency vibrating rod with a frequency of 100-200 Hz. The vibrating rod is inserted into the lower layer by 10-20 cm, and the single vibration time is 20-40 s.

7. The rockfill dam concrete panel joint structure according to claim 1, characterized in that: A copper sheet water stop is arranged at the interface between the hydraulic ECC material layer and the conventional concrete. The copper water stop is connected by double-sided lap welding, and the lap length is not less than 20 mm.

8. The rockfill dam concrete panel joint structure according to claim 1, characterized in that: The width of the induced seam is 20-40 cm.

9. The construction method of the rockfill dam concrete panel joint structure according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Cut the mortar cushion layer and emulsified asphalt layer below the concrete joint to form an induced joint; (2) Clean the induced joints and seal them with sealing materials to form a sealing layer inside the joints. The sealing position should be flush with the bottom of the adjacent concrete panel. (3) Roughen the adjacent poured conventional concrete surface to a roughness greater than 2 mm and rinse it clean; (4) Use the full-section paving method to continuously and uninterruptedly construct hydraulic ECC materials to eliminate construction joints caused by long intervals; (5) After pouring, maintenance and insulation should be carried out.

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