Double-layer geomembrane core wall rockfill dam structure and construction method

Abstract

The present invention relates to a double-layer geomembrane core wall rockfill dam structure and a construction method. The purpose of the present invention is to provide a double-layer geomembrane core wall rockfill dam structure and a construction method with superior anti-seepage performance and reliability. The technical solution of the present invention is: a double-layer geomembrane core wall rockfill dam structure, characterized in that: the rockfill dam has a double-layer geomembrane anti-seepage core wall structure; the double-layer geomembrane anti-seepage core wall structure is sequentially provided with an upstream sand cushion layer, an upstream geomembrane, a middle silt layer, a downstream geomembrane and a downstream sand cushion layer from upstream to downstream. The present invention is applicable to the field of water conservancy and hydropower engineering.

Description

Technical Field

[0001] The invention relates to a double-layer geomembrane core wall rockfill dam structure and a construction method, which are applicable to the field of water conservancy and hydropower engineering. Background Art

[0002] Geomembrane has the advantages of excellent anti-seepage performance, strong deformation ability and low investment. Designing a safe and reliable geomembrane core wall dam will be an excellent technical solution for rockfill dams built on weak foundation layers or with weak soil. However, geomembranes are fragile items and are more likely to be damaged during construction. Moreover, as a core wall set in the middle of the dam body, there is a problem that it cannot be repaired. Therefore, when using geomembranes as anti-seepage core walls, it is necessary to deal with possible damage problems during construction and operation, and have sufficient reliability. Summary of the invention

[0003] The technical problem to be solved by the present invention is: in view of the above-mentioned existing problems, a double-layer geomembrane core wall rockfill dam structure and a construction method with excellent anti-seepage performance and reliability are provided.

[0004] The technical solution adopted by the present invention is: a double-layer geomembrane core wall rockfill dam structure, characterized in that: the rockfill dam has a double-layer geomembrane anti-seepage core wall structure;

[0005] The double-layer geomembrane anti-seepage core wall structure is provided with an upstream sand cushion layer, an upstream geomembrane, a middle silt layer, a downstream geomembrane and a downstream sand cushion layer in sequence from upstream to downstream.

[0006] A geomembrane separation zone is arranged between the upstream geomembrane and the downstream geomembrane along the elevation to separate the upstream and downstream geomembranes into a plurality of independent hydraulic units.

[0007] The upstream geomembrane and the downstream geomembrane are arranged in a broken line shape along the elevation direction.

[0008] The double-layer geomembrane anti-seepage core wall structure is located on the foundation corridor in the rockfill dam, the lower ends of the upstream geomembrane and the downstream geomembrane in the double-layer geomembrane anti-seepage core wall structure are anchored on the top surface of the foundation corridor, and the upper end of the downstream geomembrane is laid along the middle silt layer to the upstream geomembrane and welded to the upstream geomembrane.

[0009] A protective sand layer is provided between the top surface of the downstream geomembrane and the crest structure of the rockfill dam.

[0010] The dam body of the rockfill dam is composed of the upstream rockfill area, the upstream dam body transition area, the upstream dam body anti-filtration cushion area, the double-layer geomembrane anti-seepage core wall structure, the downstream dam body anti-filtration cushion area, the downstream dam body transition area, the rockfill drainage area and the downstream rockfill area from upstream to downstream;

[0011] The upstream rockfill area, upstream dam body transition area, upstream dam body filter cushion area, downstream dam body filter cushion area, downstream dam body transition area, rockfill drainage area and downstream rockfill area are all located on the foundation structure, and the foundation structure includes a basic filter layer and a basic transition layer located above the basic filter layer.

[0012] A construction method of the double-layer geomembrane core wall rockfill dam structure is characterized by:

[0013] Excavate and construct the dam foundation cover layer, and excavate the foundation corridor pit along the anti-seepage line;

[0014] pouring foundation gallery;

[0015] Roll the dam foundation covering layer to form the foundation surface of the dam body;

[0016] The double-layer geomembrane anti-seepage core wall structure and the upstream and downstream dam body anti-filtration cushion layer areas are constructed in layers, and the thin layer is compacted and pressed; the upstream and downstream geomembranes are laid upward at a certain angle to the horizontal plane. After each laying at a certain elevation, the turning direction of the geomembrane is changed to form a zigzag shape that keeps going back and forth;

[0017] When the double-layer geomembrane anti-seepage core wall structure and its upstream and downstream dam body anti-filtration cushion areas are laid to a certain height, start to fill the upstream and downstream dam body filling materials, and keep the filling surface of the core wall structure and the anti-filtration cushion areas on both sides always higher than the outer dam body filling materials; the dam body filling materials include the basic anti-filtration layer, the basic transition layer, the upstream rockfill area, the upstream dam body transition area, the upstream dam body anti-filtration cushion area, the downstream dam body anti-filtration cushion area, the downstream dam body transition area, the rockfill drainage area, and the downstream rockfill area;

[0018] During the construction of the core wall structure, filter cushion area and dam body filling material, the geomembrane dividing strip is welded between the upstream and downstream geomembranes according to the set elevation;

[0019] Laying the downstream geomembrane along the top surface of the middle silt layer to the upstream geomembrane and welding it to the upstream geomembrane;

[0020] Lay a protective sand layer above the downstream geomembrane and construct the dam crest structure.

[0021] The beneficial effects of the present invention are as follows: the present invention adopts a double-layer geomembrane anti-seepage structure to greatly improve the reliability of geomembrane anti-seepage; adopts geomembrane dividing strips arranged at intervals along the elevation to carry out anti-seepage segmentation treatment, so that the anti-seepage core wall forms a number of independent hydraulic units, reducing the risk of forming a seepage channel after the two layers of geomembranes are damaged at the same time; fills the interior of the upstream and downstream geomembranes with silt, utilizes the self-healing function of the silt, certain anti-seepage performance and the anti-filtration protection function of the downstream sand cushion layer and the downstream anti-filtration cushion layer, and reduces the risk of forming a concentrated seepage channel.

[0022] The present invention gives full play to the advantages of the strong deformation ability of the geomembrane and the good anti-seepage effect of the material itself. Through structural design and the coordinated use of multiple materials, the overall reliability of the anti-seepage core wall is greatly increased, thereby greatly reducing the mechanical performance requirements of the dam on the foundation and filling materials, reducing the technical difficulty and engineering investment of soft foundation and soft rock dam construction, and promoting the development of green hydraulic construction technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A typical cross-sectional view of an embodiment.

[0024] Figure 2 Schematic diagram of the structure of the double-layer geomembrane anti-seepage core wall structure in the embodiment.

[0025] Figure 3 Schematic diagram of the bottom end of the double-layer geomembrane anti-seepage core wall structure in the embodiment.

[0026] Figure 4 It is a schematic diagram of the top of the double-layer geomembrane anti-seepage core wall structure in the embodiment.

[0027] In the figure: 1. bedrock; 2. dam foundation cover layer; 3. foundation filter layer; 4. foundation transition layer; 5. protective sand layer; 6. upstream rockfill area; 7. upstream dam body transition zone; 8. upstream dam body filter cushion area; 9. double-layer geomembrane anti-seepage core wall structure; 9-1. upstream sand cushion layer; 9-2. upstream geomembrane; 9-3. geomembrane separation zone; 9-4. middle silt layer; 9-5. downstream geomembrane; 9-6. downstream sand cushion layer; 10. downstream dam body filter cushion area; 11. downstream dam body transition zone; 12. rockfill drainage area; 13. downstream rockfill area; 14. anti-seepage anchoring mechanism; 16. foundation corridor; 17. wave-breaking wall; 18. dam top transition material and dam top pavement structure. DETAILED DESCRIPTION

[0028] This embodiment is a double-layer geomembrane core wall rockfill dam structure. The bedrock of the dam foundation is buried deep, the dam foundation cover layer is thick and relatively weak, and the rockfill dam is directly located on the dam foundation cover layer. There is a problem of large deformation of the foundation and the dam body. By arranging a double-layer geomembrane anti-seepage core wall structure in the middle of the dam body of the rockfill dam, safe and reliable flexible anti-seepage is achieved to adapt to large deformation.

[0029] The rockfill dam in this embodiment includes a foundation gallery arranged on the foundation covering layer of the dam. The bottom of the foundation gallery is appropriately excavated, and appropriate foundation reinforcement measures are taken to control the settlement and deformation of the foundation gallery to be uniform, so that large uneven settlement will not occur, which will lead to problems such as gallery cracking and waterstop tensile failure. Generally, a structural joint is set every 10 to 15 meters in the foundation gallery, and a waterstop is set in the joint.

[0030] In this example, the loose surface layer of the dam foundation cover and the humus soil layer are excavated and compacted by a roller before setting up the foundation structure, which includes a foundation filter layer and a foundation transition layer that are set up in sequence.

[0031] In this embodiment, the dam body of the zoned rockfill dam is composed of the upstream rockfill area, the upstream dam body transition area, the upstream dam body anti-filtration cushion area, the double-layer geomembrane anti-seepage core wall structure, the downstream dam body anti-filtration cushion area, the downstream dam body transition area, the rockfill drainage area and the downstream rockfill area from upstream to downstream, and the double-layer geomembrane anti-seepage core wall structure is located in the middle of the dam body. In this example, a dam crest structure is provided on the top of the dam body, and the dam crest structure includes a wave-breaking wall located above the normal water storage level of the dam crest, a dam crest transition material and a dam crest pavement structure.

[0032] In this example, the double-layer geomembrane anti-seepage core wall structure is located on the foundation corridor below. The core wall structure includes an upstream sand cushion layer, an upstream geomembrane, a middle silt layer, a downstream geomembrane and a downstream sand cushion layer from upstream to downstream.

[0033] The cross-sections of the upstream geomembrane and the downstream geomembrane along the elevation direction are in a broken line shape (large deformation adaptability). The lower ends of the upstream and downstream geomembranes are anchored on the foundation corridor below through the anti-seepage anchoring mechanism. The left and right ends of the upstream and downstream geomembranes are anchored on the left and right banks of the rockfill dam through the anti-seepage anchoring mechanism. The upper end of the downstream geomembrane is laid along the top surface of the middle silt layer to the upstream geomembrane and welded. The upper end of the upstream geomembrane is anchored to the upper wave-breaking wall through the anti-seepage anchoring mechanism. In this case, after laying a protective sand layer on the surface of the downstream geomembrane on the top surface of the middle silt layer, a dam top transition material and a dam top road were constructed.

[0034] In this embodiment, a geomembrane separator is arranged between the upstream and downstream geomembranes at a certain elevation. The upstream end of the geomembrane separator is welded to the upstream geomembrane, and the downstream end is welded to the downstream geomembrane. The left and right ends of the geomembrane separator are respectively anchored to the left and right banks of the rockfill dam through an anti-seepage anchoring mechanism.

[0035] The specific construction method of this embodiment is as follows:

[0036] Construct the dam foundation covering layer, remove the loose soil and humus on the foundation surface within the dam foundation covering layer, and excavate the foundation pit of the foundation corridor along the anti-seepage line according to the foundation corridor size and soil slope stability requirements;

[0037] After the foundation pit is treated with foundation and foundation anti-seepage treatment, the foundation gallery is poured, and installation space for the anti-seepage anchor mechanism is reserved at the top of the foundation gallery;

[0038] Roll the foundation surface of the dam foundation covering layer to form the foundation surface of the dam body;

[0039] Construct the anti-seepage anchoring mechanism between the upstream and downstream geomembranes and the bottom of the riverbed and on both sides. The height of the anchoring on both sides is generally controlled to be 2 rolling layers thick, and appropriate support measures are taken to prevent the geomembrane from hanging and being damaged due to lack of soil support at the anchoring parts on both sides.

[0040] The double-layer geomembrane anti-seepage core wall structure and the upstream and downstream dam body anti-filtration cushion layer areas are constructed in layers, and non-roller is used for thin layer tamping construction; the upstream and downstream geomembranes are laid upward at an angle of 45° to the horizontal plane. After each upward laying to a certain height, the turning direction of the geomembrane is changed to form a broken line shape that continuously turns back and forth;

[0041] When the double-layer geomembrane anti-seepage core wall structure and its upstream and downstream dam body anti-filtration cushion areas are laid to a certain height, start filling the upstream and downstream dam body filling materials, and continue filling at intervals to keep the filling surface of the double-layer geomembrane anti-seepage core wall structure and its upstream and downstream dam body anti-filtration cushion areas always higher than the outer dam body filling materials until the bottom elevation of the dam top wave-breaking wall; the dam body filling materials include foundation anti-filtration layer, foundation transition layer, upstream rockfill area, upstream dam body transition area, upstream dam body anti-filtration cushion area, downstream dam body anti-filtration cushion area, downstream dam body transition area, rockfill drainage area and downstream rockfill area.

[0042] During the construction of the core wall structure, filter cushion area and dam body fill, the geomembrane separation strip is welded between the upstream and downstream geomembranes according to the set elevation;

[0043] The upstream geomembrane exposed on the dam top is protected by a reserved anti-seepage anchoring mechanism, and a wave-breaking wall combined with the reserved anti-seepage anchoring mechanism is constructed above it;

[0044] Lay the upper end of the downstream geomembrane along the horizontal plane corresponding to the bottom elevation of the wave-breaking wall to the upstream geomembrane, weld it to the upstream geomembrane and anchor it on the wave-breaking wall;

[0045] A protective sand layer is laid on the surface of the downstream geomembrane, and then the dam top transition material and dam top road are constructed by layered rolling.

[0046] In this embodiment, the foundation anti-seepage treatment can adopt anti-seepage wall, curtain grouting or a combination of the two according to the foundation conditions and anti-seepage requirements. When the foundation anti-seepage treatment adopts curtain grouting for anti-seepage treatment, curtain grouting construction is carried out at an appropriate time after the dam body is filled to a certain elevation.

Claims

1. A double-layer geomembrane core wall rockfill dam structure, characterized in that: The rockfill dam has a double-layer geomembrane anti-seepage core wall structure (9); The double-layer geomembrane anti-seepage core wall structure (9) is provided with an upstream sand cushion layer (9-1), an upstream geomembrane (9-2), a middle silt layer (9-4), a downstream geomembrane (9-5) and a downstream sand cushion layer (9-6) in sequence from upstream to downstream; A geomembrane separation zone (9-3) is provided between the upstream geomembrane (9-2) and the downstream geomembrane (9-5) along the elevation, and is used to separate the upstream and downstream geomembranes (9-5) into a plurality of independent hydraulic units; The upstream geomembrane (9-2) and the downstream geomembrane (9-5) are arranged in a broken line shape along the elevation direction; The double-layer geomembrane anti-seepage core wall structure (9) is located on a foundation gallery (16) in a rockfill dam, and the lower ends of the upstream geomembrane (9-2) and the downstream geomembrane (9-5) in the double-layer geomembrane anti-seepage core wall structure (9) are anchored on the top surface of the foundation gallery (16). After the double-layer geomembrane anti-seepage core wall structure (9) is laid to the bottom elevation of the wave-breaking wall (17), the downstream geomembrane (9-5) is laid upstream along the bottom elevation of the wave-breaking wall (17), and is welded to the upstream geomembrane (9-2) and then anchored on the wave-breaking wall (17); A protective sand layer (5) is provided between the top surface of the downstream geomembrane (9-5) and the crest structure of the rockfill dam.

2. The double-layer geomembrane core wall rockfill dam structure according to claim 1 is characterized in that: The dam body of the rockfill dam comprises, from upstream to downstream, an upstream rockfill area (6), an upstream dam body transition area (7), an upstream dam body anti-filtration cushion area (8), the double-layer geomembrane anti-seepage core wall structure (9), a downstream dam body anti-filtration cushion area (10), a downstream dam body transition area (11), a rockfill drainage area (12) and a downstream rockfill area (13); The upstream rockfill area (6), the upstream dam body transition area (7), the upstream dam body filter cushion area (8), the downstream dam body filter cushion area (10), the downstream dam body transition area (11), the rockfill drainage area (12) and the downstream rockfill area (13) are all located on a foundation structure, and the foundation structure comprises a foundation filter layer (3) and a foundation transition layer (4) located above the foundation filter layer (3).

3. A construction method for a double-layer geomembrane core rockfill dam structure according to any one of claims 1 to 2, characterized in that: Construct the dam foundation cover layer and excavate the foundation corridor (16) foundation pit along the anti-seepage line; pouring the foundation gallery (16); Roll the dam foundation covering layer to form the foundation surface of the dam body; The double-layer geomembrane anti-seepage core wall structure (9) and the upstream and downstream dam body anti-filtration cushion layer areas (10) are constructed in layers, and the thin layer is compacted and constructed; the upstream and downstream geomembranes are laid upward at a certain angle to the horizontal plane, and after each laying to a certain elevation, the turning direction of the geomembrane is changed, so that the geomembrane forms a zigzag shape that keeps going back and forth; When the double-layer geomembrane anti-seepage core wall structure (9) and its upstream and downstream dam body filter cushion areas are laid to a certain height, the upstream and downstream dam body filling materials are started to be filled, and the filling surface of the core wall structure and the filter cushion areas on both sides is kept higher than the outer dam body filling materials; the dam body filling materials include a basic filter layer (3), a basic transition layer (4), an upstream rockfill area (6), an upstream dam body transition area (7), an upstream dam body filter cushion area (8), a downstream dam body filter cushion area (10), a downstream dam body transition area (11), a rockfill drainage area (12), and a downstream rockfill area (13); During the construction of the core wall structure, filter cushion area and dam body fill, the geomembrane separation strip (9-3) is welded between the upstream and downstream geomembranes according to the set elevation; Laying the downstream geomembrane (9-5) along the horizontal plane corresponding to the bottom elevation of the wave-breaking wall (17) to the upstream geomembrane (9-2), welding it to the upstream geomembrane (9-2), and then anchoring it on the wave-breaking wall (17); A protective sand layer (5) is laid above the downstream geomembrane (9-5) and the dam top structure is constructed.

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