A method for one-time casting of dam overflow surface

Abstract

This invention provides a method for one-time pouring of the dam overflow surface. The dam or overflow section is divided into a modified concrete zone, a first roller-compacted concrete zone, a second roller-compacted concrete zone, and an erosion-resistant and wear-resistant concrete zone, based on the upstream to downstream cross-section. Construction is carried out in the modified concrete zone, the first roller-compacted concrete zone, and the second roller-compacted concrete zone. After the second roller-compacted concrete is constructed, its right end slopes downwards to form a step on the surface overflow surface. Then, the erosion-resistant and wear-resistant concrete zone is poured in one go. The construction process of the erosion-resistant and wear-resistant concrete zone includes the following steps: S1, foundation treatment; S2, rebar tying; S3, formwork installation; S4, concrete pouring; S5, formwork removal; S6, concrete finishing; S7, concrete curing. This method for one-time pouring of the dam overflow surface improves the construction quality of the dam overflow surface by pouring the erosion-resistant and wear-resistant concrete in one go after the roller-compacted concrete construction is completed.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering construction technology, and in particular to a method for one-time pouring of the overflow surface of a dam. Background Technology

[0002] Roller-compacted concrete gravity dams typically incorporate spillway sections. These spillway gravity dams must both impound and discharge water, meeting not only stability and strength requirements but also ensuring smooth water flow and preventing cavitation damage. The spillway surface is located in a high-speed flow zone, and numerous hydropower projects have experienced spillway surface failures. Therefore, the bonding between the erosion-resistant and abrasion-resistant surface concrete and the dam body concrete is crucial; the surface smoothness and control of surface porosity significantly impact the operational safety of the spillway surface.

[0003] In current construction practices involving roller-compacted concrete (RCC) and spillway sections with erosion-resistant and wear-resistant concrete, the RCC portion of the dam body is typically formed integrally before the spillway concrete is poured. This method has the following drawbacks: long intermittent joints are generated as the spillway and RCC rise synchronously, leading to a need for improvement in construction quality. Summary of the Invention

[0004] The purpose of this invention is to provide a one-time pouring construction method for the overflow surface of a dam or overflow dam section, where the main concrete is roller-compacted concrete and the overflow surface is erosion-resistant and wear-resistant concrete, so as to improve the construction quality of the dam overflow surface.

[0005] To achieve the above objectives, the technical solution adopted by this invention is a one-time pouring construction method for the overflow surface of a dam. Its structural feature is that the dam or overflow section is divided into a modified concrete zone, a first roller-compacted concrete zone, a second roller-compacted concrete zone, and an erosion-resistant and wear-resistant concrete zone according to the upstream to downstream cross-section. Construction is carried out on the modified concrete zone, the first roller-compacted concrete zone, and the second roller-compacted concrete zone. The top surfaces of these zones are then smoothed and cured. After the construction of the second roller-compacted concrete zone, its right end slopes downwards to form a step on the surface overflow surface. Finally, the erosion-resistant and wear-resistant concrete zone is poured in one go. The construction process of the erosion-resistant and wear-resistant concrete zone includes the following steps:

[0006] S1. Basic treatment: roughen the surface of the overflow surface step and the transverse seam of the surface hole.

[0007] S2. Reinforcement binding: Bind all structural reinforcements in the erosion-resistant and wear-resistant concrete zone.

[0008] S3. Template installation: During the preparation period, install all the templates for the erosion-resistant and wear-resistant concrete area on the overflow surface step of the surface hole.

[0009] S4. Concrete pouring: During pouring, a chute is set up in the slab surface. The chute is arranged below the reinforcing steel in the slab. The chute moves upward as the pouring operation progresses, pouring the concrete in one go.

[0010] S5. Formwork removal: The formwork will be removed after the poured concrete has reached the required strength for demolding.

[0011] S6. Concrete finishing is carried out using a continuous follow-up method;

[0012] S7. Concrete curing.

[0013] Furthermore, the concrete gradation of the modified concrete zone is two-stage; the concrete gradation of the first roller-compacted concrete zone is two-stage; the concrete gradation of the second roller-compacted concrete zone is three-stage; the concrete gradation of the impact-resistant and wear-resistant concrete zone is two-stage, and the thickness of the impact-resistant and wear-resistant concrete zone is 25cm to 35cm.

[0014] Furthermore, the slump of the erosion-resistant and wear-resistant concrete zone is 70mm to 90mm.

[0015] Furthermore, in step S1, the roughening depth of the surface of the overflow surface step and the transverse seam of the surface hole is 3cm to 5cm.

[0016] Furthermore, in step S2, when binding the reinforcing bars, support bars are set on each surface of the hole to fix the curved reinforcing bars, and template bars are installed on the curved reinforcing bars.

[0017] Furthermore, in step S3, the arc-shaped surface below the turtle-back of the overflow surface is constructed using a brand-new steel formwork splicing method, and the wide tail pier area is filled with modified steel formwork.

[0018] Furthermore, in step S4, the distance between the chute discharge port and the pouring surface is <2m.

[0019] Furthermore, in step S5, the demolding strength is ≥0.2 MPa.

[0020] Furthermore, in step S6, the concrete pouring adopts the method of pouring and demolding simultaneously. After the lower concrete strength reaches the demolding strength, the formwork can be removed piece by piece upwards. After the formwork is removed, the concrete surface is immediately smoothed.

[0021] Furthermore, the concrete finish consists of multiple layers of concrete.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. After the roller-compacted concrete construction is completed, impact-resistant and wear-resistant concrete is poured again. The impact-resistant and wear-resistant concrete on the overflow surface is poured in one piece without construction joints, resulting in a complete shape, a smoother structural surface, and smoother water flow.

[0024] Second, by using multiple finishing and curing processes, cracks in the overflow surface concrete can be avoided, thus ensuring the construction quality of the overflow surface.

[0025] Third, the present invention provides a construction method for one-time pouring of the dam overflow surface, which does not affect the preparation time of roller-compacted concrete, can accelerate the rising speed of roller-compacted concrete, and save a lot of labor, time, materials, equipment resources and water and electricity resources. Under the premise of ensuring the quality of concrete pouring, it shortens the construction period and greatly reduces the construction cost. Attached Figure Description

[0026] Figure 1 This is a flowchart of a one-time pouring construction method for the overflow surface of a dam according to the present invention;

[0027] Figure 2 This is a detailed flowchart of a method for one-time pouring of the dam overflow surface in one embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the lateral partitioning of the dam overflow section in one embodiment of the present invention;

[0029] Figure 4 This is a schematic cross-sectional view of the overflow section of a dam in one embodiment of the present invention.

[0030] In the diagram: 1. Modified concrete zone; 2. First roller-compacted concrete zone; 3. Second roller-compacted concrete zone; 4. Impact-resistant and wear-resistant concrete zone; 5. Surface bore step. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. For ease of description, the terms "upper," "lower," "left," and "right" used below only indicate that they correspond to the upper, lower, left, and right directions in the accompanying drawings and do not limit the structure.

[0032] This embodiment uses a dam as an example. The dam is a roller-compacted concrete gravity dam with a maximum height of 106m, a crest elevation of EL1481.00, and a crest length of 231.5m. The dam has five spillway sections (sections 4 to 8). The spillway surface of the surface spillway sections is the flow surface, and the concrete is HF erosion-resistant and wear-resistant concrete, located from 0+007.392 to 0+032.50 downstream of the dam. The elevation ranges from EL1432.67 to EL1458.92. The width is 13.5m, and the average thickness is 3m. The shape is arc-shaped, and the equation of its shape is y = 0.047366 x 1.85.

[0033] like Figures 1-4 As shown in this embodiment, a one-time pouring construction method for the spillway surface of a dam is characterized by dividing the pouring area of ​​the dam or spillway section into a modified concrete zone 1, a first roller-compacted concrete zone 2, a second roller-compacted concrete zone 3, and an impact-resistant and wear-resistant concrete zone 4 according to the upstream to downstream cross section.

[0034] In this embodiment, the concrete in the modified concrete zone 1 is C. 180 The concrete is grade 20W8F100, with a secondary mix design and a thickness of 80cm. The concrete in the first roller-compacted concrete zone 2 is C. 180 The concrete in the second roller-compacted concrete zone 3 is of grade C, with a mix design of 20W8F100 and a thickness of 400cm. 180 15W4F50 three-grade aggregate. The concrete in the impact-resistant and abrasion-resistant concrete zone 4 is C. 28 The concrete is a 30W8F100 two-component mix, and the thickness of the erosion-resistant and wear-resistant concrete zone 4 is 30cm. The slump of the concrete in the erosion-resistant and wear-resistant concrete zone 4 is 70mm to 90mm.

[0035] Construction is carried out on three zones: modified concrete zone 1, first roller-compacted concrete zone 2, and second roller-compacted concrete zone 3. The top surfaces of these zones are then finished and cured. After construction of the second roller-compacted concrete zone 3, its right end slopes downwards to form a step on the surface overflow surface. Finally, the impact-resistant and wear-resistant concrete zone 4 is poured in a single operation. The construction process of the impact-resistant and wear-resistant concrete zone 4 includes the following steps:

[0036] S1. Foundation Treatment: Before pouring concrete below the turtle-back shape of the overflow surface of the surface hole, the surface step surface 5 and the transverse seam of the surface hole need to be roughened. In this embodiment, the roughening depth of the surface step surface 5 and the transverse seam of the surface hole is 3cm to 5cm.

[0037] S2. Reinforcement binding: Bind all structural reinforcements in the erosion-resistant and wear-resistant concrete zone.

[0038] In this embodiment, during rebar tying, support bars are installed on each surface of the bore to fix the curved rebar, and template bars are installed on the curved rebar. The template bars use C28 rebar, arranged vertically and horizontally, and welded into a single unit. Support bars also use C28 rebar, and a nut is welded to the short support bars. The nut is used for template adjustment to control the shape, ensuring no external exposure of the support bars later.

[0039] S3. Template installation: During the preparation period, install all the templates for the erosion-resistant and wear-resistant concrete zone 4 on the overflow surface step of the surface hole.

[0040] In this embodiment, the arc-shaped surface below the overflow surface (the turtle-back shape) is constructed using spliced ​​steel formwork of new P1015 and P3015 models. Modified steel formwork is used for joint filling in the wide tail pier area. Formwork hoisting is primarily performed using a 30t cable crane and a TC7035B fixed tower crane. Before erecting the formwork, a surveying engineer lays out control points according to the drawings. The formwork is erected strictly according to these points, with control points set for important structures. During the erection process, the formwork position is checked, and any deviations are immediately corrected to ensure the installation deviations meet the specifications. During formwork installation, joints are smooth and even, without misalignment. Local unevenness of the formwork is less than 2mm, and gaps on the board surface are no greater than 2mm. Release agent is applied evenly; if the values ​​exceed the specified limits, correction or grouting is performed to prevent grout leakage and ensure the appearance quality of the poured concrete.

[0041] S4. Concrete pouring: Two chutes are set up in the slab surface during pouring. The chutes are arranged below the reinforcing bars in the slab. The chutes move upward as the pouring operation progresses, pouring the concrete in one go.

[0042] In this embodiment, step S4 is as follows: Impact-resistant and wear-resistant concrete is transported using a 25t dump truck and poured using a 30t cable crane or tower crane. A chute is installed inside the formwork, positioned below the reinforcing steel bars. The chute moves upwards as pouring progresses, with the chute outlet less than 2m from the pouring surface. When concrete enters the formwork, a baffle is used to protect the downstream formwork to prevent concrete from falling onto it, and a designated person directs the crane's unloading. φ100mm and φ70mm vibrators and a plate vibrator are used for compaction. Vibration is performed promptly during pouring to prevent uneven compaction. The interlayer between the curved formwork and the reinforcing mesh is vibrated with a vibrator, supplemented by manual tapping of the formwork to listen for sound and prevent voids from forming inside the formwork. After each layer of formwork is poured, it is tapped to compact any gaps. The start time of each layer of formwork pouring is recorded for easy formwork removal.

[0043] The overflow surface of the surface outlet is curved, and its shape is controlled by standardized templates and reinforcing bars. On-site construction personnel, in conjunction with surveyors, mark the shape lines of the reinforcing bars and templates on both sides of the gate pier. Construction personnel must strictly adhere to these two shape lines during the rebar tying and template installation processes. Simultaneously, during concrete pouring, the shape is continuously monitored and corrected as needed. The templates are fixed using bolt sleeves, allowing for adjustments to the template shape at any time.

[0044] Impact-resistant and wear-resistant concrete has a low slump and poor fluidity, therefore, its transportation must be rapid. Vehicles should be equipped with sunshades during transport to avoid direct sunlight. The on-site pouring speed must be strictly controlled. Detailed technical instructions should be given to the site before construction, and dedicated personnel should be assigned to supervise and manage the process, controlling the material delivery speed and timing. The slump of the concrete delivered to the placement site should be monitored in real time to ensure good workability and meet the requirements for on-site concrete pouring and finishing.

[0045] S5. Formwork Removal: The formwork is removed after the poured concrete reaches the required strength for demolding. In this embodiment, the demolding strength is ≥0.2 MPa.

[0046] In this embodiment, step S5 is as follows: the formwork can only be removed when the concrete strength under the formwork reaches 0.2 MPa (2-3 hours). Since the concrete pouring time varies for each layer of formwork, the time it takes to reach 0.2 MPa is different. The formwork can only be removed when the strength of the subsequently poured concrete also reaches 0.2 MPa. The initially set concrete surface is then smoothed. Ideally, when the concrete strength reaches 0.2 MPa, pressing the concrete surface with your hand should leave a fingerprint, and the mortar on the concrete surface should not be sticky to the touch.

[0047] S6. Concrete finishing: Concrete finishing is carried out in a continuous, follow-up manner. Concrete pouring is carried out while formwork is being removed, and the concrete finishing consists of multiple layers.

[0048] In this embodiment, step S6 specifically involves the following process: Concrete pouring is carried out while formwork is being removed. Considering that curved concrete pouring is prone to air bubbles that affect appearance, the formwork is removed piece by piece upwards when the lower concrete strength reaches 0.2 MPa. The surface is then manually smoothed using tools such as wooden scrapers and steel trowels on a finishing frame. Taking winter concrete pouring as an example, the formwork removal and finishing time in winter is 8 hours. First, a long scraper is used to level the surface, then a wooden trowel is used for rough finishing. After the surface stops bleeding (before the initial setting of the concrete), a steel trowel is used to smooth and polish the concrete surface, employing a three-stage finishing process. The first finishing primarily aims to make the concrete surface flat and smooth. The first finishing is performed after formwork removal (finishing should be done promptly based on the principle that the concrete surface leaves a mark when pressed by hand; the finishing should be accurate and smooth, and the height difference of the overflow surface should be controlled within the design range). The second and third finishing primarily aim to further compact and smooth the concrete.

[0049] S7. Concrete Curing: Overflow surface concrete should be cured with running water to keep the surface constantly moist. First, cover with plastic film to retain moisture, then cover with geotextile and sprinkle with water to prevent early plastic cracking due to water loss. The curing period should be no less than 28 days. During the curing period, a designated person should be responsible for overseeing the process and maintaining proper curing records.

[0050] This embodiment of a method for one-time pouring of dam overflow surface involves pouring erosion-resistant and abrasion-resistant concrete a second time after the roller-compacted concrete (RCC) construction. The erosion-resistant and abrasion-resistant concrete of the overflow surface is poured integrally without construction joints, resulting in a complete shape, a smoother structural surface, and smoother water flow. Through multiple finishing and curing processes, cracks in the overflow surface concrete can be avoided, ensuring the construction quality of the overflow surface. This one-time pouring method for dam overflow surface does not affect the preparation time of the RCC, can accelerate the rising speed of the RCC, and saves significant labor, time, material, equipment, and water and electricity resources. It shortens the construction period and greatly reduces construction costs while ensuring the quality of concrete pouring.

[0051] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present embodiments by those skilled in the art will fall within the scope defined by the appended claims.

Claims

1. A method for one-time casting of the overflow surface of a dam, characterized in that, The dam or spillway section is divided into three sections from upstream to downstream: the modified concrete zone (1), the first roller-compacted concrete zone (2), the second roller-compacted concrete zone (3), and the erosion-resistant and wear-resistant concrete zone (4). Construction of the modified concrete zone (1), the first roller-compacted concrete zone (2), and the second roller-compacted concrete zone (3) is carried out. The top surfaces of the modified concrete zone (1), the first roller-compacted concrete zone (2), and the second roller-compacted concrete zone (3) are smoothed and cured. After the construction of the second roller-compacted concrete zone (3), the top right end of the zone slopes downward to form a step for the overflow surface of the surface hole. Finally, the erosion-resistant and wear-resistant concrete zone (4) is poured in one go. The construction process of the erosion-resistant and wear-resistant concrete zone (4) includes the following steps: S1. Basic treatment: roughen the surface of the overflow surface step (5) and the transverse seam of the surface hole. S2. Reinforcement binding: Bind all structural reinforcements in the erosion-resistant and wear-resistant concrete zone; When binding reinforcements, set support bars on the surface of each surface hole step to fix the arc reinforcements, and install template bars on the arc reinforcements. S3. Template installation: During the preparation period, all templates of the anti-erosion and wear-resistant concrete area (4) will be installed on the overflow surface step of the surface hole; the arc surface below the turtle back of the overflow surface will be constructed using new steel template splicing, and the wide tail pier will be filled with modified steel templates. S4. Concrete pouring: During pouring, a chute is set up in the slab surface. The chute is arranged below the reinforcing steel in the slab. The chute moves upward as the pouring operation progresses, pouring the concrete in one go. S5. Formwork removal: The formwork will be removed after the poured concrete has reached the required strength for demolding. S6. Concrete finishing is carried out in a continuous follow-up manner. Concrete pouring is carried out by pouring and demolding at the same time. After the lower concrete strength reaches the demolding strength, the formwork can be removed piece by piece upwards. After the formwork is removed, the concrete surface is immediately finished. S7. Concrete curing.

2. The method for one-time casting of the dam overflow surface according to claim 1, characterized in that, The concrete gradation of the modified concrete zone (1) is secondary; the concrete gradation of the first roller-compacted concrete zone (2) is secondary; the concrete gradation of the second roller-compacted concrete zone (3) is tertiary; the concrete gradation of the erosion-resistant and wear-resistant concrete zone (4) is secondary, and the thickness of the erosion-resistant and wear-resistant concrete zone (4) is 25cm~35cm.

3. The method for one-time casting of the dam overflow surface according to claim 1, characterized in that, The concrete slump of the erosion-resistant and wear-resistant concrete zone (4) is 70mm~90mm.

4. The method for one-time casting of the dam overflow surface according to claim 1, characterized in that, In step S1, the roughening depth of the surface of the overflow surface step (5) and the surface of the transverse seam is 3cm~5cm.

5. The method for one-time casting of the dam overflow surface according to claim 1, characterized in that, In step S4, the distance between the chute discharge port and the pouring surface is <2m.

6. The method for one-time casting of the dam overflow surface according to claim 1, characterized in that, In step S5, the demolding strength is ≥0.2 MPa.

7. A method for one-time casting of the overflow surface of a dam according to any one of claims 1-6, characterized in that, In step S6, the concrete finish is a multi-layered concrete finish.

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