Seepage prevention structure and construction method for homogeneous earth dam heightening project

Abstract

The present invention discloses an anti-seepage structure and construction method for the heightening project of a homogeneous earth dam. The anti-seepage structure includes an anti-seepage layer on the upstream slope of the dam body after heightening, inclined grouting curtains on the left and right banks, anti-seepage membrane connection piers at the upstream dam toe position, and dam foundation grouting galleries on both sides of the river valley, an anti-seepage wall and a grouting curtain under the piers. The gallery is used for the construction of the grouting pipes of the vertical grouting curtains on both banks of the dam foundation; the pier is used for the connection between the anti-seepage structure below the dam foundation and the geomembrane. The anti-seepage structure of the homogeneous earth dam heightening project of the present invention has good flexibility and flexible construction; the embedded connection of the geomembrane at the four perimeters makes the connection part with the grouting curtain not easy to crack and seep water; fully considering the river valley morphology, an anti-seepage structure is formed by an inclined grouting curtain and a vertical grouting curtain, enhancing the anti-seepage effect of the dam after heightening.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy projects, and in particular to an anti-seepage structure and construction method for the heightening project of homogeneous earth dams. Background Art

[0002] A dam is a water retaining structure that intercepts the flow of rivers and channels to raise the water level or regulate the flow rate, and is widely used for flood control, water supply, irrigation, hydropower generation, improving shipping, etc. China is a country with extremely rich water resources, but at the same time, it is also very short of water. In order to make full use of water resources, a huge number of homogeneous earth dams have been built in China. At present, on the one hand, the flood control capacity has been reduced due to the sedimentation in the reservoir areas of the homogeneous earth dams built in the early stage, and on the other hand, due to the requirements of economic development, it is necessary to expand the capacity of the reservoir. Therefore, it is necessary to heighten the original homogeneous earth dam body. After heightening, the flood control and anti-seepage grades of the dam are correspondingly improved, and the original anti-seepage structure of the old dam can no longer meet the requirements. Therefore, we need to re-arrange the anti-seepage structure.

[0003] Generally, the anti-seepage structure of a dam includes a cut-off wall arranged along the dam axis or an anti-seepage layer structure arranged along the slope surface, etc. For this new dam type of homogeneous earth dam heightening, since the new and old dam bodies need to undergo a consolidation deformation process after heightening, the anti-seepage structure of arranging a cut-off core wall along the dam axis cannot be constructed immediately after the dam body is filled. The cut-off core wall has good anti-seepage ability, but poor adaptability to dam body deformation. Therefore, it is necessary to wait for a time when the deformation is stable, which results in a lag in the construction period.

[0004] As a flexible material, geomembrane has been continuously applied to various anti-seepage projects such as earth-rock dams. It has the advantages of good anti-seepage performance, strong adaptability to deformation, fast construction speed and low project cost. However, the thickness of the geomembrane used for anti-seepage of earth-rock dams is very thin, and some areas are prone to damage during the construction process. After the dam is impounded, leakage will occur in these areas. At the same time, in the existing geomembrane anti-seepage structure, improper treatment is often carried out on both sides of the dam body, resulting in around-dam leakage, and water leakage also occurs at the connection of the dam toe, which poses a threat to the project safety. Summary of the Invention

[0005] In view of the above problems, the present invention provides an anti-seepage structure and construction method for the heightening project of homogeneous earth dams, which have the advantages of short construction period and good anti-seepage effect.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: An anti-seepage structure for the heightening project of homogeneous earth dams, comprising:

[0007] The composite geomembrane impermeable layer located on the upstream slope of the dam body after heightening, the inclined grouting curtains located on the left and right banks of the dam body, the impermeable membrane connection pier at the upstream dam toe position, the dam foundation grouting galleries on both sides of the river valley, the impervious wall below the impermeable membrane connection pier, and the vertical grouting curtain below the impervious wall, where

[0008] The dam foundation grouting gallery is used for the construction of the grouting pipes of the vertical grouting curtains on both banks of the dam foundation;

[0009] The impermeable membrane connection pier is used for connecting the impervious structure below the dam foundation with the geomembrane;

[0010] The top of the impervious wall is flexibly connected to the lower part of the impervious membrane connection pier.

[0011] The composite geomembrane impermeable layer has 6 layers, which are, from bottom to top: the lower cushion layer, the first geomembrane layer, the middle cushion layer, the second geomembrane layer, the upper cushion layer, and the concrete block or dry rubble stone protection layer.

[0012] The lower cushion layer is poured with 6 - 10 cm thick polyurethane permeable concrete, and both the middle cushion layer and the upper cushion layer are composed of 6 - 10 cm thick fine - grained sandy clay.

[0013] The geomembrane in the impermeable layer is a two - fabric - one - membrane geomembrane.

[0014] The inclined grouting curtain is formed by grouting through the curtain grouting pipes reserved in the concrete piers poured on both sides of the dam bank.

[0015] The cross - section of the dam foundation grouting gallery is arched, the inner wall of the dam foundation grouting gallery is shotcreted, and the vertical grouting pipes are arranged on the bottom platform of the dam foundation grouting gallery.

[0016] Both the impermeable membrane connection pier and the impervious wall are formed by casting reinforced concrete.

[0017] The connection of the geomembrane on both sides of the dam bank is as follows: the first geomembrane layer is embedded in the concrete piers poured on both sides of the dam bank, and asphalt layers for bonding and waterproofing are laid on the upper and lower surfaces of the geomembrane;

[0018] The second geomembrane layer adopts the groove anchoring method with grooves reserved on the surface of the pier, and concrete is poured on the surface of the grooves.

[0019] The connection between the impermeable membrane connection pier and the geomembrane is as follows: the first geomembrane layer is embedded in the impermeable membrane connection pier, and asphalt layers for bonding and waterproofing are laid on the upper and lower surfaces of the first geomembrane layer; the second geomembrane layer adopts the groove anchoring method with grooves reserved on the surface of the impermeable membrane connection pier, and concrete is poured on the surface of the grooves.

[0020] The present invention further discloses a seepage prevention construction method for the homogeneous earth dam heightening project. Based on the seepage prevention structure for the homogeneous earth dam heightening project, the method includes the following steps: (1) Excavate the foundation of the grouting gallery on both sides of the river valley and the connection pier of the geomembrane at the upstream dam toe. Spray concrete on the inner wall of the grouting gallery of the dam foundation, and arrange the grouting pipes for the vertical grouting curtain on both sides of the dam foundation.

[0021] Set the impervious wall operation platform on the bottom surface of the foundation of the connection pier of the geomembrane. First, dig the trench to construct the impervious wall and carry out curtain grouting under the wall. Construct the pier at the top of the wall. Leave a groove between the impervious wall and the connection pier of the geomembrane, and fill the groove between the impervious wall and the pier with impervious flexible material. Set the water-stop copper sheet at the lower edge of the groove. First, construct a certain height of the connection pier of the geomembrane. After the first layer of geomembrane is embedded, then construct the remaining height.

[0022] (2) While constructing the connection pier of the geomembrane, start constructing the concrete piers on both sides of the dam bank. The piers are constructed in two stages. In the first stage, construct a certain height. After the first layer of geomembrane is embedded, then construct the remaining part.

[0023] (3) Carry out peeling correction and rolling treatment on the upstream slope of the heightened dam body, and pour the lower cushion layer along the entire upstream slope, and cure for 2 - 3 days.

[0024] (4) After the curing of the lower cushion layer, lay the first layer of geomembrane along the slope of the lower cushion layer, and carry out joint welding and weld quality inspection. First, lay a layer of asphalt with a thickness of 5 - 10 cm on the plane of the connection pier of the geomembrane, embed the first layer of geomembrane, then lay another layer of asphalt with a thickness of 5 - 10 cm, and then construct the remaining height of the connection pier of the geomembrane, and reserve a groove on the top surface.

[0025] The connection between the first layer of geomembrane and the concrete pier also adopts the same treatment method. When constructing the remaining part of the pier,

[0026] embed the PVC pipe to form a reserved curtain grouting hole; the first layer of geomembrane should reserve a certain expansion length at the connection position to be made into a corrugated fold to adapt to deformation.

[0027] (5) After the first layer of geomembrane is laid, lay the middle cushion layer along the surface of the entire first layer of geomembrane, lay the second layer of geomembrane on the surface of the middle cushion layer, and at the same time, carry out curtain grouting to both sides of the dam bank through the reserved curtain grouting pipes in the piers on both sides of the dam bank to form the inclined grouting curtain, and carry out grouting through the vertical grouting curtain grouting pipes in the grouting gallery of the dam foundation to form the vertical impervious curtain.

[0028] (6) After grouting, embed the second layer of geomembrane into the grooves reserved on the surfaces of the connection pier of the geomembrane and the pier respectively, and pour concrete on the surface of the groove for sealing. Excavate a groove on the dam top, embed the two layers of geomembrane, and pour concrete on the surface of the groove for sealing.

[0029] (7) After the second-layer geomembrane is laid, a top cushion layer is laid on the entire surface of the second-layer geomembrane. After the top cushion layer is laid, concrete blocks or dry rubble stone protection layers are laid on the surface of the top cushion layer.

[0030] The present invention has the following beneficial effects: (1) For the new dam type of homogeneous earth dam heightening, since the new and old dam bodies need to undergo a consolidation deformation process after heightening, the anti-seepage structure provided by the present invention is a flexible structure with strong deformation adaptability and can change together with the dam body. Therefore, it is not necessary to wait until the dam body deformation is stable before construction. The anti-seepage structure can be arranged after the new dam filling is completed, with flexible construction and good flexibility of the anti-seepage structure.

[0031] (2) The present invention fully considers the valley shape of the dam, connects the anti-seepage structure with the valley bedrock as a whole, and can effectively prevent seepage around the dam. Through the anti-seepage layer on the upstream slope of the dam body after heightening, the inclined grouting curtains on the left and right banks, the cut-off wall at the dam foundation, and the vertical anti-seepage curtain, an overall anti-seepage structure is formed, enhancing the water-stop effect of the entire dam after heightening.

[0032] (3) The anti-seepage layer of the present invention adopts two layers of geomembranes, which can ensure that even if one layer of geomembrane is damaged during use, water leakage will not occur, and the service life is long. The geomembranes are embedded and anchored at the four perimeters, so that the anti-seepage layer and the dam top, the curtains on both sides of the dam bank, and the cut-off wall form a closed anti-seepage structure, effectively solving the problem of easy cracking and water leakage at the peripheral joints of the anti-seepage membrane. A channel is left between the cut-off wall and the pier, and the channel is filled with impermeable flexible materials, which can significantly adjust the deformation incoordination between the cut-off wall and the pier. Description of the Drawings

[0033] Figure 1 It is a schematic structural diagram of the anti-seepage structure of the present invention for the homogeneous earth dam heightening project.

[0034] Figure 2 It is a plan layout diagram of the anti-seepage structure of the present invention for the homogeneous earth dam heightening project.

[0035] Figure 3 It is a typical cross-sectional diagram of the anti-seepage structure of the present invention for the homogeneous earth dam heightening project.

[0036] Figure 4 It is an embedded connection diagram of the geomembrane and the concrete piers poured on both sides of the dam bank in the present invention.

[0037] Among them: 1. Raising the dam body; 2. Anti-seepage layer; 3. Concrete blocks or dry block stone protective layer; 4. Dam bank piers; 5. Anti-seepage membrane connecting piers; 6. Anti-seepage wall; 7. Vertical grouting pipe; 8. Dam foundation grouting gallery; 9. Inclined grouting pipe; 10. Vertical grouting curtain; 11. Inclined grouting curtain; 12. New dam body; 13. Dam top groove; 14. Lower cushion layer; 15. First layer of geomembrane; 16. Middle cushion layer; 17. Second layer of geomembrane; 18. Upper cushion layer; 19. Old dam body with homogeneous soil; 20. Pier surface groove; 21. Asphalt layer; 22. Waterproof flexible material; 23. Water-stop copper sheet; 24. Alluvial layer; 25. Bedrock; 26. Pier surface groove. DETAILED DESCRIPTION

[0038] like Figures 1 to 4 As shown, an anti-seepage structure for homogeneous earth dam heightening engineering includes a composite geomembrane anti-seepage layer 2 on the upstream slope of the heightened dam body 1, inclined grouting curtains 11 on the left and right banks, an anti-seepage membrane connecting pier 5 at the upstream dam foot position and a dam foundation grouting gallery 8 on both sides of the river valley, an anti-seepage wall 6 under the pier and a vertical grouting curtain 10. In order to improve the reliability of the anti-seepage membrane, the anti-seepage layer is composed of 6 layers: a lower cushion layer 14, a first geomembrane layer 15, a middle cushion layer 16, a second geomembrane layer 17, an upper cushion layer 18, and a concrete block or dry block stone protective layer 3; the dam foundation grouting gallery 8 is used for the construction of vertical grouting curtains and vertical grouting pipes 7 on both sides of the dam foundation; the anti-seepage membrane connecting pier 5 is used to connect the anti-seepage structure below the dam foundation with the first geomembrane layer 15 and the second geomembrane layer 17.

[0039] The lower cushion layer 14 in the anti-seepage layer 2 is cast with 6-10 cm thick polyurethane permeable concrete, and the middle cushion layer 16 and the upper cushion layer 18 are composed of 6-10 cm thick fine-grained sandy clay; the geomembrane is a two-cloth-one-film geomembrane.

[0040] The inclined grouting curtain 11 is formed by grouting through the curtain grouting pipes 9 reserved in the concrete piers 4 cast on both sides of the dam bank, and the inclined grouting curtain penetrates into the 5Lu boundary line in the mountain.

[0041] The cross section of the dam foundation grouting gallery 8 is arched, the inner wall of the gallery is sprayed with concrete, and the vertical grouting pipe 7 is arranged on the platform at the bottom of the gallery.

[0042] An impermeable wall 6 is arranged under the impermeable membrane connection pier 5, and a vertical grouting curtain 10 is formed by grouting through a vertical grouting pipe 7 under the impermeable wall. The vertical grouting curtain 10 penetrates through the alluvial layer 24 and penetrates into the 5Lu boundary of the bedrock 25. The top of the impermeable wall is flexibly connected to the lower part of the impermeable membrane connection pier 5. The impermeable membrane connection pier and the impermeable wall are both formed by pouring reinforced concrete.

[0043] Further, the connection treatment of the geomembrane on both sides of the dam bank is as follows: The first layer of geomembrane 15 is embedded in the concrete piers 4 poured on both sides of the dam bank, and asphalt layers 21 with a thickness of 5 - 10 cm are laid on the upper and lower surfaces of the first layer of geomembrane 15; The second layer of geomembrane 17 adopts the groove anchoring method of reserving the groove 26 on the surface of the pier, and concrete is poured on the surface of the groove.

[0044] Further, the connection treatment of the anti-seepage membrane connection pier 5 and the geomembrane is as follows: The first layer of geomembrane 15 is embedded in the pier, and asphalt layers 21 with a thickness of 5 - 10 cm are laid on the upper and lower surfaces of the first layer of geomembrane 15; The second layer of geomembrane 17 adopts the groove anchoring method of reserving the groove 20 on the surface of the pier, and concrete is poured on the surface of the groove.

[0045] Further, the treatment of the two layers of geomembrane on the dam crest adopts the groove anchoring method of excavating the groove 13 on the top surface of the dam, and concrete is poured on the surface of the groove.

[0046] The construction method of the anti-seepage structure of the homogeneous earth dam heightening project includes the following steps: (1) Excavate the foundations of the grouting galleries 8 on both sides of the river valley and the anti-seepage membrane connection piers 5 at the upstream dam toe. Spray concrete on the inner wall of the gallery, and arrange the vertical grouting pipes 7 of the vertical grouting curtain on both banks of the dam foundation; Set the anti-seepage wall operation platform on the bottom surface of the anti-seepage membrane connection pier foundation, first excavate the groove to construct the anti-seepage wall 6 and conduct curtain grouting under the wall, construct the anti-seepage membrane connection pier at the top of the wall, leave a channel between the anti-seepage wall and the anti-seepage membrane connection pier, and fill the channel between the anti-seepage wall and the anti-seepage membrane connection pier with the impermeable flexible material 22, and set the water stop copper sheet 23 at the lower edge of the channel. The anti-seepage membrane connection pier is constructed to a certain height first, and after the first layer of geomembrane 15 is embedded, the remaining height is constructed.

[0047] (2) While constructing the anti-seepage membrane connection pier 5, the concrete piers 4 on both sides of the dam bank also start construction. The piers are constructed in two stages. In the first stage, a certain height is constructed, and after the first layer of geomembrane 15 is embedded, the remaining part is constructed; (3) Carry out peeling correction and rolling treatment on the upstream slope of the heightened dam body, pour the polyurethane permeable concrete lower cushion layer 14 along the entire upstream slope, and cure for 2 - 3 days;

[0048] (4) After the curing of the lower cushion layer 14 is completed, lay the first layer of geomembrane 15 along the slope of the cushion layer, and conduct joint welding and weld quality inspection. First, lay a layer of asphalt with a thickness of 5 - 10 cm on the plane of the anti-seepage membrane connection pier 5, embed the first layer of geomembrane 15, then lay another layer of asphalt with a thickness of 5 - 10 cm, and then construct the remaining height of the anti-seepage membrane connection pier, and reserve the groove 20 on the surface of the pier on the top surface. The connection between the first layer of geomembrane 15 and the concrete pier 4 also adopts the same treatment method. When constructing the remaining part of the pier, pre-buried PVC pipes are formed into inclined grouting pipes 9.

[0049] At the connection position, the geomembrane should be reserved with a certain expansion length to form corrugated wrinkles to adapt to deformation.

[0050] (5) After the first layer of geomembrane 15 is laid, the middle cushion layer 16 is laid along the entire surface of the geomembrane, and the second layer of geomembrane 17 is laid on the surface of the middle cushion layer. At the same time, curtain grouting is carried out on both sides of the dam through the inclined grouting pipes 9 reserved in the piers 4 on both sides of the dam bank to form an inclined grouting curtain 11, and grouting is carried out through the vertical grouting pipes 7 in the dam foundation grouting gallery 8 to form a vertical grouting curtain 10.

[0051] (6) After grouting, the second layer of geomembrane 17 is respectively embedded into the grooves reserved on the surfaces of the anti-seepage membrane connection piers 5 and the piers, and concrete is poured on the surface of the grooves for sealing. The dam top groove 13 is excavated on the dam top, and the two layers of geomembrane are embedded, and concrete is poured on the surface of the groove for sealing.

[0052] (7) After the second layer of geomembrane 17 is laid, the upper cushion layer 18 is laid along the entire surface of the second layer of geomembrane. After the upper cushion layer is laid, the concrete block or dry block stone protective layer 3 is laid on the surface of the upper cushion layer.

Claims

1. An anti-seepage construction method for the heightening project of a homogeneous earth dam, based on an anti-seepage structure for the heightening project of a homogeneous earth dam, includes: A composite geomembrane anti-seepage layer on the upstream slope of the dam body after heightening, inclined grouting curtains on the left and right banks of the dam body, anti-seepage membrane connection piers at the upstream dam toe, dam foundation grouting galleries on both sides of the river valley, a cut-off wall under the anti-seepage membrane connection piers, and a vertical grouting curtain under the cut-off wall. Among them, the dam foundation grouting gallery is used for the construction of the vertical grouting pipes of the vertical grouting curtains on both banks of the dam foundation; The anti-seepage membrane connection pier is used for connecting the anti-seepage structure below the dam foundation and the geomembrane of the anti-seepage layer; There is a flexible connection between the top of the cut-off wall and the lower part of the anti-seepage membrane connection pier; it is characterized by the following steps: (1) Excavate the foundation of the dam foundation grouting galleries on both sides of the river valley and the anti-seepage membrane connection piers at the upstream dam toe. Spray concrete on the inner wall of the dam foundation grouting gallery and arrange the vertical grouting pipes of the vertical grouting curtains on both banks of the dam foundation; Set an anti-seepage wall operation platform on the bottom surface of the foundation of the anti-seepage membrane connection pier. First, dig a trench to construct the anti-seepage wall and carry out curtain grouting under the wall. Construct the anti-seepage membrane connection pier at the top of the wall. Leave a trench between the anti-seepage wall and the anti-seepage membrane connection pier, and fill the trench between the anti-seepage wall and the anti-seepage membrane connection pier with impermeable flexible material. Set a water-stop copper sheet at the lower edge of the trench. The anti-seepage membrane connection pier is constructed to a certain height first, and after the first layer of geomembrane is embedded, the remaining height is constructed; (2) While constructing the anti-seepage membrane connection pier, the concrete piers on both sides of the dam bank also start to be constructed. The piers are constructed in two stages. The first stage is constructed to a certain height, and after the first layer of geomembrane is embedded, the remaining part is constructed; (3) Carry out peeling correction and rolling treatment on the upstream slope of the heightened dam body, pour a lower cushion layer along the entire upstream slope, and cure for 2 - 3 days; After the curing of the lower cushion layer, lay the first layer of geomembrane along the slope of the lower cushion layer, and carry out joint welding and weld quality inspection. First, lay a layer of asphalt with a thickness of 5 - 10 cm on the plane of the anti-seepage membrane connection pier, embed the first layer of geomembrane, then lay another layer of asphalt with a thickness of 5 - 10 cm, and then construct the remaining height of the anti-seepage membrane connection pier, and reserve a groove on the top surface of the pier; The connection between the first layer of geomembrane and the concrete pier also adopts the same treatment method. When constructing the remaining part of the pier, pre-embed PVC pipes to form inclined grouting pipes; the first layer of geomembrane should reserve a certain expansion length at the connection position and be made into corrugated folds to adapt to deformation; (5) After the first layer of geomembrane is laid, lay a middle cushion layer along the entire surface of the first layer of geomembrane, lay the second layer of geomembrane on the surface of the middle cushion layer, and at the same time, carry out curtain grouting to the two banks of the dam through the inclined grouting pipes reserved in the piers on both sides of the dam bank to form the inclined grouting curtain, and carry out grouting through the vertical grouting pipes in the dam foundation grouting gallery to form the vertical grouting curtain; After the grouting is completed, embed the second layer of geomembrane into the grooves reserved on the surfaces of the anti-seepage membrane connection pier and the pier respectively, pour concrete on the surface of the groove for sealing, excavate a dam top groove on the dam top, embed the two layers of geomembrane, and pour concrete on the surface of the dam top groove for sealing; After the second layer of geomembrane is laid, a top cushion layer is laid on the surface of the entire second layer of geomembrane. After the top cushion layer is laid, a concrete block or dry rubble stone protective layer is laid on the surface of the top cushion layer.

2. The anti-seepage construction method for the homogeneous earth dam heightening project according to claim 1, characterized in that, The lower cushion layer is poured with polyurethane permeable concrete with a thickness of 6 - 10 cm, and both the middle cushion layer and the top cushion layer are composed of fine-grained sandy clay with a thickness of 6 - 10 cm.

3. The anti-seepage construction method for the homogeneous earth dam heightening project according to claim 1, characterized in that, The geomembrane in the anti-seepage layer is a two-layer fabric and one-layer film geomembrane.

4. The anti-seepage construction method for the homogeneous earth dam heightening project according to claim 1, characterized in that, The cross-section of the grouting gallery of the dam foundation is arched.

5. The anti-seepage construction method for the homogeneous earth dam heightening project according to claim 1, characterized in that, Both the anti-seepage membrane connecting pier and the anti-seepage wall are formed by casting reinforced concrete.

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