Design and construction method for horizontal seepage prevention between concrete face plate and diaphragm wall of face plate dam on deep overburden layer

Abstract

The present application belongs to the technical field of earth-rock dam construction, and provides a design and construction method for horizontal seepage prevention between concrete face slab and cutoff wall of face slab dam on deep overburden layer. The steps are as follows: 1) constructing concrete face slab dam body, concrete cutoff wall, toe slab and face slab; 2) setting and constructing asphalt concrete on the lower part of toe slab on the downstream side of cutoff wall; and 3) wrapping high plastic soil and clay on the top of cutoff wall and extending horizontally to face slab. The present application designs an asphalt concrete horizontal seepage prevention layer between cutoff wall and face slab, cancels the connecting plate and the water stop joint structure between the connecting plate and the cutoff wall, sets a second horizontal seepage prevention body of asphalt concrete on the downstream side of cutoff wall and the bottom of toe slab, and simultaneously adopts double-layer seepage prevention design of clay and asphalt concrete, so that the risk of seepage damage of seepage prevention body can be further reduced.

Description

Technical Field

[0001] This invention belongs to the field of earth-rock dam construction technology, and relates to the design and construction method of horizontal seepage prevention between the concrete panel of a dam with a thick overburden layer and the seepage barrier wall. Background Technology

[0002] With the continuous advancement of hydropower development, the dam site conditions for water conservancy projects in my country are becoming increasingly complex, making dam construction on overburden foundations "unavoidable." Currently, my country has several completed and planned high earth-rock dam projects, including Shiziping, Huangjinping, Xiabandi, Luding, Pangduo, Yele, and Altash, all with overburden depths reaching or exceeding 100 meters. The seepage barrier is a crucial component of the dam, making it particularly important to research design and construction technologies to further improve the safety of seepage prevention systems in earth-rock dams with deep overburden.

[0003] In concrete-faced rockfill dams built on overburden foundations, the cutoff wall is positioned upstream of the dam body, avoiding direct impact from the dam's weight and minimizing the risk of damage. However, traditional concrete-faced rockfill dams have a complex seepage control system, consisting of a concrete face, toe slab, connecting slab, cutoff wall, and water-stop joints between them. Due to the significant difference in modulus between the overburden foundation soil and the concrete cutoff wall, excessive shear deformation at the water-stop joints between the connecting slab and the cutoff wall can easily occur under reservoir water pressure, leading to damage. Therefore, addressing the problem of excessive deformation of the water-stop joints in traditional overburden-faced rockfill dams, which causes dam leakage and subsequent seepage failure, is crucial. Summary of the Invention

[0004] To address the problem of excessive deformation and damage to the waterstop joints in traditional concrete-faced rockfill dams with overburden layers due to the large difference in modulus between the overburden foundation soil and the anti-seepage wall concrete, this invention provides a design and construction method for horizontal seepage prevention between the concrete face and the anti-seepage wall of a dam with a deep overburden layer. This method eliminates the design of connecting plates and waterstop joints, and adopts a double-layer seepage prevention design of clay and asphalt concrete, effectively improving the safety of the seepage prevention body.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A design and construction method for horizontal seepage prevention between the concrete panel and the cutoff wall of a deep overburden dam is disclosed. The method involves wrapping the top of the concrete cutoff wall 2 with high-plasticity soil 9 and clay 10, and reserving an extra-high (to accommodate the insertion of the cutoff wall) horizontal seepage prevention design between the cutoff wall and the panel. This eliminates the need for connecting plates and their water-stop joints with the cutoff wall. Simultaneously, a second layer of asphalt concrete horizontal seepage prevention is installed on the downstream side of the cutoff wall and at the bottom of the toe slab, improving the safety of the seepage prevention structure. The method includes the following steps:

[0007] 1) An asphalt concrete horizontal anti-seepage layer is installed between the downstream face of the concrete anti-seepage wall 2 and the lower part of the concrete panel 6, and is constructed using the vibratory compaction method. The bottom of the asphalt concrete horizontal anti-seepage layer is the cover layer 3.

[0008] 2) The portion of the concrete anti-seepage wall that extends above the cover layer 3 is wrapped with high-plastic soil 9 and clay 10 in sequence, and extends horizontally to the concrete panel 6. It is constructed using the vibratory compaction method.

[0009] The specific implementation process includes the following steps:

[0010] 1) The dam body is constructed by filling the rockfill material layer by layer using the vibratory compaction method until the top of the dam is reached.

[0011] 2) At the top elevation EL1 of the overburden 3, establish a construction site centered on the central axis of the concrete cutoff wall 2, where the downstream face of the concrete cutoff wall 2 is l from the toe slab 5. Using a grab bucket or hydraulic milling machine, excavate the overburden 3 into a trench with a width of d1 along the axis of the concrete cutoff wall 2, and use mud slurry for wall protection. Then, pour ordinary concrete using a vertical tremie pipe method to complete the main construction of the concrete cutoff wall 2. The main body of the concrete cutoff wall 2 is a first-stage cutoff wall with a width of d1.

[0012] 3) The top h1 area of ​​the concrete cutoff wall 2 is designed as a trapezoid, serving as the second-phase cutoff wall. The top width is d2. A formwork is installed, and the construction is completed using the cast-in-place method. Wherein, d2 is less than d1.

[0013] 4) Lay asphalt concrete 4 horizontally from the downstream side of the concrete anti-seepage wall 2 to the bottom of the concrete panel 6. The thickness is h3 and the width is d3, which serves as the horizontal asphalt concrete anti-seepage layer.

[0014] 5) A toe plate 5 is set at the bottom of the concrete panel 6, and the toe plate 5 is placed on top of the asphalt concrete 4. Specifically: a formwork is set up, the toe plate 5 is constructed by cast-in-place method, the concrete panel 6 is poured by slip form construction method, and the perimeter joint 7 between the concrete panel 6 and the bedrock / toe plate 5 and the vertical joint of the concrete panel 6 are completed.

[0015] 6) A filter layer 8 with a height of h4 and a width of d4 is set on the upstream side of the concrete anti-seepage wall 2, and is constructed by vibration compaction.

[0016] 7) Centered on the central axis of the concrete cutoff wall 2, a high-plasticity soil zone 9 with a width of d5 and a height of h5 is set in the area where the cutoff wall 2 is higher than the overburden layer 3 (the top surface of the high-plasticity soil zone 9 is located above the top surface of the second-phase cutoff wall). The high-plasticity soil 9 extends downstream to the concrete toe slab 5, with an extension height of h2. The extension zone is located above the asphalt concrete 4. That is, the bottom surface of the high-plasticity soil zone 9 on the upstream side of the concrete cutoff wall 2 is in contact with the filter layer 8, and the bottom surface of the high-plasticity soil zone 9 on the downstream side is in contact with the asphalt concrete 4. A clay zone 10 with a height of h6 is set outside the high-plasticity soil, extending downstream to the concrete panel 6 and horizontally upstream to the filter layer 8. The end is protected by the filter layer 8, and the construction is carried out by vibratory compaction. The upper surface of the clay zone 10 is located above the high-plasticity soil zone 9.

[0017] Furthermore, the thickness of the clay 10 must meet the requirements for seepage damage and seepage flow.

[0018] Furthermore, the horizontal length of the asphalt concrete 4 on the downstream side of the concrete cutoff wall 2 must exceed the downstream side of the toe slab 5 and extend upwards until it contacts the concrete panel 6. That is, the asphalt concrete 4 is laid inside the dam body rockfill 1 at the right side of the toe slab 3 and below the concrete panel 6.

[0019] The beneficial effects of this invention are as follows:

[0020] Compared with existing technologies, the advantages of this invention are that it proposes a design and construction method for horizontal seepage prevention between the concrete panel of a deep overburden dam and the cutoff wall. This eliminates the need for the connecting plate and the water-stop joint structure between the concrete panel dam and the toe slab / cutoff wall, resulting in higher safety for the double-layer horizontal seepage prevention system. This is mainly reflected in the fact that highly plastic soil and clay can effectively adapt to uneven settlement caused by the difference in modulus between the overburden and the concrete cutoff wall, eliminating the need for the traditional water-stop structure between the downstream side of the cutoff wall and the connecting plate. The trapezoidal design at the top of the cutoff wall ensures a tight fit between the highly plastic soil and the cutoff wall during settlement, and the double-layer seepage prevention design of asphalt concrete and clay further reduces the risk of seepage damage to the seepage prevention system. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the design scheme of the overburden dam seepage prevention system of the present invention;

[0022] Numbers in the diagram: 1-Dam body rockfill; 2-Concrete cutoff wall; 3-Covering layer; 4-Asphalt concrete; 5-Toe slab; 6-Concrete panel; 7-Peripheral joint; 8-Filter layer; 9-High plasticity soil; 10-Clay; EL1-Top elevation of the overburden layer; l-Distance between the downstream side of the cutoff wall and the upstream side of the toe slab; d1-Width of the cutoff wall; h1-Height of the top zone of the cutoff wall; d2-Top width of the cutoff wall; h2-Height of the extension zone of the high plasticity soil; d3-Width of the asphalt concrete; h3-Thickness of the asphalt concrete; d4-Width of the filter layer; d3-Thickness of the filter layer; d5-Width of the high plasticity soil; h5-Thickness of the high plasticity soil; h6-Thickness of the clay. Detailed Implementation

[0023] The present invention will be further described below with reference to specific implementation examples.

[0024] The following are some engineering examples:

[0025] Taking an asphalt concrete-faced dam with an overburden layer as an engineering case study, the top elevation of the overburden layer is 2950m, the dam crest elevation is 3030m, the dam height is 80m, and the dam crest width is 10m. The upstream slope of the dam body is 1:1.6, and the downstream slope is 1:1.8. The thickness of the concrete face varies from the dam crest to the dam base by 0.4 + 0.0035h, where h is the height from the dam crest in meters. A reinforced concrete toe slab, 4.0m wide and 1.2m high, is installed at the bottom of the face. A suspended cutoff wall is used for seepage prevention at the dam foundation, with a depth of 150m and a thickness of 1.2m. The axis of the cutoff wall is 12m from the toe slab. The cutoff wall is connected to the toe slab and the face using asphalt concrete and clay as a horizontal seepage barrier. The specific operation process is described below:

[0026] 1) The dam rockfill material is filled layer by layer and constructed using the vibratory compaction method until the top of the dam is reached.

[0027] 2) At an elevation of 2950m above the top of the overburden, a construction site is established with the central axis of the concrete cutoff wall 2 as the center. The downstream side of the cutoff wall 2 is 12m from the toe slab 5. Using a grab bucket or hydraulic milling machine, the overburden 3 is excavated into a trench with a width of 1.2m along the axis of the concrete cutoff wall 2, and mud slurry is used for wall protection. Then, ordinary concrete is poured using a vertical tremie pipe method to complete the main construction of the cutoff wall 2. The main body of the concrete cutoff wall 2 is also a first-phase cutoff wall with a width of 1.2m.

[0028] 3) The top 5m of the concrete cutoff wall 2 is designed as a trapezoid, serving as the second-phase cutoff wall. The top width is 0.4m. Formwork is set up, and the construction is completed by cast-in-place method.

[0029] 4) Lay asphalt concrete 4 horizontally from the downstream side of the seepage barrier to the bottom of the panel, with a thickness of 0.2m and a width of 20m;

[0030] 5) Set up the template, construct the toe slab 5 using the cast-in-place method, pour the concrete panel 6 using the slipform construction method, and complete the construction of the perimeter joint 7 between the panel and the bedrock / toe slab and the vertical joint of the panel.

[0031] 6) A filter layer 8 with a height of 2m and a width of 20m is set on the upstream side of the anti-seepage wall, and the construction is carried out by vibration rolling method.

[0032] 7) Centered on the central axis of the concrete anti-seepage wall 2, a 4m wide and 5m high high-plasticity soil zone 9 is set up, extending downstream to the concrete toe slab with a height of 1.5m. A clay zone 10, 20m high, is set up outside the high-plasticity soil zone, extending downstream to the concrete panel and horizontally upstream to the filter layer. A filter layer is installed at the end for protection. Vibratory compaction is used for construction. The above embodiments only illustrate the implementation of the present invention and should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A design and construction method for horizontal seepage prevention between the concrete panel of a deep overburden dam and the cutoff wall, characterized in that, The design and construction method involves wrapping the top of a concrete cutoff wall with highly plastic soil and clay, and designing a horizontal asphalt concrete cutoff layer between the cutoff wall and the concrete panel. This eliminates the need for connecting plates and their water-stop joints with the cutoff wall. Simultaneously, a horizontal asphalt concrete cutoff layer is set on the downstream side of the cutoff wall and at the bottom of the toe slab to improve the safety of the cutoff structure. Specifically: a horizontal asphalt concrete cutoff layer is set between the downstream face of the concrete cutoff wall and the lower part of the concrete panel, constructed using a vibratory compaction method; the bottom of the horizontal asphalt concrete cutoff layer is a cover layer; the portion of the top of the concrete cutoff wall exceeding the cover layer is successively wrapped with highly plastic soil and clay, with the highly plastic soil extending horizontally to the concrete panel. This horizontal extension section forms the second horizontal cutoff structure, constructed using a vibratory compaction method. The specific steps include: 1) The dam body is constructed by filling the rockfill material layer by layer and compacting it with a vibratory roller until the top of the dam is reached; 2) At elevation EL1 above the overburden, establish a construction site centered on the central axis of the concrete cutoff wall. Using a grab bucket or hydraulic milling machine, excavate a trench along the axis of the concrete cutoff wall, with a width of [missing information]. d 1. Mud slurry is used for wall protection, followed by pouring ordinary concrete using a vertical tremie pipe method to complete the main construction of the concrete cutoff wall. The main body of the concrete cutoff wall is the first-phase cutoff wall, with a width of [missing information]. d 1; 3) The top of the concrete cutoff wall is designed in a trapezoidal shape, serving as the secondary cutoff wall, with a top width of [missing information]. d 2. Set up formwork and complete the construction using the cast-in-place method; among which, d 2 less than d 1; 4) Lay asphalt concrete horizontally from the downstream side of the concrete cutoff wall to the bottom of the concrete panel as a horizontal asphalt concrete cutoff layer; the horizontal length of the asphalt concrete on the downstream side of the concrete cutoff wall must exceed the downstream side of the toe slab and extend upward until it contacts the concrete panel. 5) A toe slab is set at the bottom of the concrete panel and is placed on top of the asphalt concrete. Specifically: a formwork is set up, the toe slab is constructed using the cast-in-place method, the concrete panel is poured using the slipform construction method, and the construction of the perimeter joint between the concrete panel and the toe slab, as well as the construction of the vertical joint inside the concrete panel are completed. 6) A filter layer is installed on the upstream side of the concrete anti-seepage wall, and the construction method is vibratory compaction. 7) Centered on the central axis of the concrete cutoff wall, a high-plasticity soil zone is set at the top, extending horizontally downstream to the concrete toe slab. This extended zone forms the second horizontal cutoff layer and is located above the asphalt concrete. That is, the bottom surface of the high-plasticity soil zone on the upstream side of the concrete cutoff wall contacts the filter layer, and the bottom surface of the high-plasticity soil zone on the downstream side contacts the asphalt concrete. A clay zone is set outside the high-plasticity soil zone, extending downstream to the concrete panel and horizontally upstream to the filter layer. The end is protected by a filter layer, and the construction is carried out using the vibratory compaction method.

2. The design and construction method for horizontal seepage prevention between the concrete panel of a deep overburden dam and the cutoff wall, as described in claim 1, is characterized in that... The thickness of the clay zone must meet the requirements for resistance to seepage damage and seepage flow.

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