Construction method of earth-rock dam crest with seepage prevention wall poured in stages

Abstract

This invention discloses a method for constructing the crest of an earth-rock dam using a phased pouring of the cutoff wall. It is applicable to earth-rock dams with a wave wall on the water-facing side of the crest, a retaining wall on the water-repellent side, a first-stage cutoff wall within the dam body, and guide walls on both sides of the first-stage cutoff wall. First, the top of the first-stage cutoff wall is shaped into a trapezoidal structure with gradually decreasing spacing on both sides. Then, the guide walls on both sides are removed. Next, a second-stage cutoff wall, with its top surface at the same height as the dam crest, is poured into the groove above the first-stage cutoff wall. Finally, geogrids are laid on the top surface of the second-stage cutoff wall and the top surface of the dam soil, and the roadbed and surface layer are constructed to complete the construction. This invention eliminates uneven settlement of the dam crest and cracking of the road surface caused by inconsistent concrete strength within the dam body, improving the seepage prevention effect of the cutoff wall, ensuring project quality, and simultaneously guaranteeing normal passage for personnel and vehicles on the dam crest.

Description

Technical Field

[0001] This invention relates to the field of earth-rock dam construction technology, and in particular to a method for constructing the top of an earth-rock dam by pouring the anti-seepage wall in stages. Background Technology

[0002] In the reinforcement and strengthening of earth-rock dams, concrete cutoff walls are typically used to address seepage and stability issues in the dam body and foundation. Based on materials, concrete cutoff walls can be classified into plastic concrete and reinforced concrete. Plastic concrete cutoff walls have a certain degree of flexibility, lower strength, and better bonding with the dam soil, making them more commonly used in seepage control for earth dams. To ensure the borehole inclination and construction quality, guide walls are usually installed on both sides of the cutoff wall before pouring the plastic concrete. Typically, the guide walls are about 1m deep and 0.5m wide, using normal concrete structures with a strength generally not less than C20. However, the strength of plastic concrete cutoff walls is generally not greater than 5MPa. Therefore, after the cutoff wall is poured, uneven bonding between the soft and hard surfaces of the dam crest structure can occur, leading to cracks in the road surface above the dam crest, affecting traffic and project safety. However, since the outer side of the guide wall is usually made of soil, it is tightly bonded to the dam soil after pouring. If it is forcibly removed, it will easily affect the seepage prevention effect of the anti-seepage wall and the engineering quality of the earth-rock dam. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for constructing the crest of an earth-rock dam using a staged pouring of a cutoff wall that exhibits good anti-settlement, anti-cracking, and seepage-proof properties. Specifically, the following technical solution can be adopted:

[0004] The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages, as described in this invention, is applicable to earth-rock dams where a wave wall is installed on the water-facing side of the dam crest, a retaining wall is installed on the water-repellent side of the dam crest, a first-stage seepage barrier wall is installed inside the dam body, and guide walls are installed on both sides of the first-stage seepage barrier wall. The method includes the following steps:

[0005] First, the top of the first-stage cutoff wall is shaped into a trapezoidal structure with the spacing between the two sides gradually decreasing. Then, the guide walls on both sides are removed. Next, the second-stage cutoff wall is poured in the groove above the first-stage cutoff wall, with the top surface of the second-stage cutoff wall being the same height as the top surface of the dam. Finally, geogrids are laid on the top surface of the second-stage cutoff wall and the top surface of the dam soil, and the roadbed and surface layer are constructed to complete the construction.

[0006] The steps for dismantling the guide walls on both sides are as follows:

[0007] S1, a road grooving machine is used to groove along the outer sides of the two guide walls to separate the sides of the guide walls from the dam soil.

[0008] S2, using a pneumatic pick and gas cutting equipment to make a horizontal cut at the bottom of the guide wall on the downstream side, and using the bucket teeth of an excavator to grab the top of the guide wall and push it towards the first-stage anti-seepage wall in the middle, so that the downstream guide wall tilts along the trapezoidal structure at the top of the first-stage anti-seepage wall to separate it from the dam soil, and then it is lifted out by a crane.

[0009] S3: A pneumatic pick and gas cutting equipment are used to make a horizontal cut at the bottom of the guide wall on the upstream side. The top of the guide wall is then gripped by the bucket teeth of an excavator and pushed towards the first-stage anti-seepage wall in the middle. This causes the upstream guide wall to tilt along the trapezoidal structure at the top of the first-stage anti-seepage wall, thus separating it from the dam soil. Finally, it is lifted out by a crane.

[0010] The first-stage anti-seepage wall is set near the upstream side of the dam body, and the first-stage anti-seepage wall is a plastic concrete wall with a thickness of 0.4~0.8m.

[0011] The guide walls are symmetrically arranged on both sides of the top of the first-phase seepage barrier wall, and the width of each guide wall is 0.55~0.65m and the depth is 1m.

[0012] The second-phase seepage barrier wall is constructed from plastic concrete with a compressive strength of 1.5~2.5MPa.

[0013] The bottom surface of the second-stage cutoff wall is set at the same height as the bottom surface of the trapezoidal structure of the first-stage cutoff wall, and the width of the second-stage cutoff wall is equal to the sum of the widths of the first-stage cutoff wall and the guide wall.

[0014] The geogrid includes a type A geogrid installed above the secondary seepage barrier wall, a type B geogrid installed on the top surface of the dam soil, and a type C geogrid installed at the junction of the secondary seepage barrier wall and the top surface of the dam soil.

[0015] The A-type geogrid, the B-type geogrid, and the C-type geogrid have the same height, and the aperture size of the A-type geogrid is 25×25mm, the aperture size of the B-type geogrid is 50×50mm, and the aperture size of the C-type geogrid is 20×20mm.

[0016] Both the roadbed and the surface layer are sloped downwards at a 2% gradient along the direction of water flow.

[0017] The surface layer comprises, from bottom to top, a 120mm thick 5% cement-stabilized crushed stone layer, a 6mm thick emulsified asphalt seal layer, a 50mm thick AC-16 dense-graded asphalt concrete mixture layer, and a 30mm thick AC-13 dense-graded asphalt concrete mixture layer.

[0018] The present invention provides a method for constructing the top of an earth-rock dam with a seepage barrier wall in stages. This method is convenient to construct and ensures the stability of the dam structure. First, the outer side of the guide wall is separated from the dam body. Then, by cutting the bottom and pushing the top, the guide wall is tilted onto the trapezoidal structure at the top of the first-stage seepage barrier wall, thus achieving a non-destructive separation between the guide wall and the dam body. Second, by pouring the second-stage seepage barrier wall into the groove at the top of the first-stage seepage barrier wall and by laying different types of geogrids in sections on the dam top, the uneven settlement of the dam top and cracking of the dam top road surface caused by inconsistent concrete strength within the dam body are eliminated. This improves the seepage prevention effect of the seepage barrier wall, ensures the quality of the project, and guarantees the normal passage of personnel and vehicles on the dam top. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the phased casting earth-rock dam without guide wall described in this invention.

[0020] Figure 2 yes Figure 1 Schematic diagram of the laying of the grid layer on the top of the dam.

[0021] Figure 3 yes Figure 2 Enlarged view of part A in the image.

[0022] Figure 4 yes Figure 3 BB cross-section diagram.

[0023] Figure 5 This is a structural schematic diagram of the present invention before the second-stage anti-seepage wall is poured.

[0024] Figure 6 This is a schematic diagram of the structure of the present invention for repairing the first-stage seepage barrier wall and excavating a separation trench on the side of the guide wall.

[0025] Figure 7 This is a schematic diagram of the structure in this invention where the guide wall tilts to the top of the first-phase seepage barrier. Detailed Implementation

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. These embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific construction processes are given. However, the scope of protection of the present invention is not limited to the following embodiments.

[0027] like Figure 1-7As shown, the earth-rock dam without guide walls, constructed in stages according to the present invention, includes a dam body 1. A wave wall 2 is installed on the water-facing side of the top of the dam body 1, and a retaining wall 3 is installed on the water-retaining side of the top of the dam body 1. A primary seepage barrier 4, made of plastic concrete with a thickness of 0.4~0.8m, is installed inside the dam body 1 near the upstream side. The primary seepage barrier 4 has a trapezoidal structure with gradually decreasing spacing on both sides at its top, and a secondary seepage barrier 5 is installed above it. The secondary seepage barrier 5 is constructed of plastic concrete with a compressive strength of 1.5~2.5MPa. Its top surface is at the same height as the top surface of the dam body 1, and its bottom surface is at the same height as the bottom surface of the trapezoidal structure of the primary seepage barrier 4. Its width is equal to the sum of the widths of the primary seepage barrier 4 and the original guide wall 6. The original guide walls 6 are symmetrically arranged on both sides of the top of the primary seepage barrier 4, with a width of 0.55~0.65m and a depth of 1m on each side. Type A geogrid 7 is laid above the second-phase seepage barrier 5, Type B geogrid 8 is laid on the top surface of the soil of dam body 1, and Type C geogrid 9 is laid at the junction of the second-phase seepage barrier 5 and the top surface of the soil of dam body 1. Subgrade 10 and surface layer 11 are constructed on top of Type A geogrid 7, Type B geogrid 8, and Type C geogrid 9. The heights of the aforementioned Type A geogrid 7, Type B geogrid 8, and Type C geogrid 9 are equal, and each is constructed by passing 1.5mm diameter steel wire 71 through and fixing it to 3×3mm geogrid strips 72. The aperture size of Type A geogrid 7 is 25×25mm, that of Type B geogrid 8 is 50×50mm, and that of Type C geogrid 9 is 20×20mm. Furthermore, both the subgrade 10 and surface layer 11 are sloped downwards at a 2% gradient along the water flow direction. In this embodiment, the surface layer 11 includes, from bottom to top, a 120mm thick 5% cement-stabilized crushed stone layer, a 6mm thick emulsified asphalt seal layer, a 50mm thick AC-16 dense-graded asphalt concrete mixture layer, and a 30mm thick AC-13 dense-graded asphalt concrete mixture layer.

[0028] The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages according to the present invention includes the following steps:

[0029] The first step is to repair the top surface of the first-phase seepage prevention wall (section 4):

[0030] S1, a small excavator with a bucket width of 30cm is used to excavate the first-stage anti-seepage wall 4 inside the guide wall 6 to 10cm above the design elevation (10cm protective layer is reserved).

[0031] S2, manually trim the top of the first-phase seepage barrier wall 4 to make its top a trapezoidal structure with the spacing between the two sides gradually decreasing;

[0032] The second step is to remove the guide walls on both sides:

[0033] S1. A road grooving machine is used to cut grooves 12 on the outer side of the two guide walls 6 respectively. The groove 12 is 15cm wide and the depth of the groove 12 is determined according to the depth of the guide wall 6, generally 100 to 120cm, so that the side of the guide wall 6 is separated from the dam soil.

[0034] S2, using a pneumatic pick and gas cutting equipment to make a horizontal cut at the bottom of the guide wall 6 on the downstream side, and using the bucket teeth of an excavator to grab the top of the guide wall 6 and push it towards the first-stage anti-seepage wall 4 in the middle, so that the downstream guide wall 6 tilts along the trapezoidal structure at the top of the first-stage anti-seepage wall 4 to separate it from the dam soil, and then lifts it out with a crane.

[0035] S3, using a pneumatic pick and gas cutting equipment to make a horizontal cut at the bottom of the guide wall 6 on the upstream side, and using the bucket teeth of an excavator to grab the top of the guide wall 6 and push it towards the first-stage anti-seepage wall 4 in the middle, so that the upstream guide wall 6 tilts along the trapezoidal structure at the top of the first-stage anti-seepage wall 4, achieving separation from the dam soil, and then lifting it out with a crane.

[0036] Preferably, a pneumatic pick combined with an oxy-fuel cutting device can be used to make multiple transverse cuts in the middle of the guide wall 6 to remove the longitudinal reinforcing bars and divide the guide wall 6 into sections for easy knocking down and lifting out.

[0037] The third step is to pour the second-stage seepage barrier 5, whose top surface is at the same height as the top surface of the dam body 1, into the groove above the first-stage seepage barrier 4;

[0038] The fourth step involves laying geogrids on the top surface of the second-phase seepage prevention wall 5 and the top surface of the soil of the dam body 1, constructing the roadbed 10 and the surface layer 11, and completing the construction.

[0039] The aforementioned method of removing the guide wall and pouring the anti-seepage wall effectively avoids any adverse effects on the dam's anti-seepage performance. Furthermore, by laying different types of geogrids in sections on the dam crest, phenomena such as uneven settlement of the dam crest and cracking of the dam crest road surface caused by inconsistent concrete strength within the dam structure are eliminated. This improves the anti-seepage effect of the anti-seepage wall, ensures project quality, and guarantees normal passage for personnel and vehicles on the dam crest.

[0040] It should be noted that in the description of this invention, terms such as "front," "rear," "left," "right," "vertical," "horizontal," "inner," and "outer" indicating orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

Claims

1. A method for constructing the crest of an earth-rock dam with a seepage barrier wall cast in stages, applicable to earth-rock dams where a wave wall is installed on the water-facing side of the dam crest, a retaining wall is installed on the water-repellent side of the dam crest, a first-stage seepage barrier wall is installed inside the dam body, and guide walls are installed on both sides of the first-stage seepage barrier wall, characterized in that... Includes the following steps: First, the top of the first-stage cutoff wall is shaped into a trapezoidal structure with the spacing between the two sides gradually decreasing. Then, the guide walls on both sides are removed. Next, the second-stage cutoff wall is poured in the groove above the first-stage cutoff wall, with the top surface of the second-stage cutoff wall being the same height as the top surface of the dam. Finally, geogrids are laid on the top surface of the second-stage cutoff wall and the top surface of the dam soil, and the roadbed and surface layer are constructed to complete the construction. The steps for dismantling the guide walls on both sides are as follows: S1, a road grooving machine is used to groove along the outer sides of the two guide walls to separate the sides of the guide walls from the dam soil. S2, using a pneumatic pick and gas cutting equipment to make a horizontal cut at the bottom of the guide wall on the downstream side, and using the bucket teeth of an excavator to grab the top of the guide wall and push it towards the first-stage anti-seepage wall in the middle, so that the downstream guide wall tilts along the trapezoidal structure at the top of the first-stage anti-seepage wall to separate it from the dam soil, and then it is lifted out by a crane. S3: A pneumatic pick and gas cutting equipment are used to make a horizontal cut at the bottom of the guide wall on the upstream side. The top of the guide wall is then gripped by the bucket teeth of an excavator and pushed towards the first-stage anti-seepage wall in the middle. This causes the upstream guide wall to tilt along the trapezoidal structure at the top of the first-stage anti-seepage wall, thus separating it from the dam soil. Finally, it is lifted out by a crane.

2. The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages according to claim 1, characterized in that: The first-stage anti-seepage wall is set near the upstream side of the dam body, and the first-stage anti-seepage wall is a plastic concrete wall with a thickness of 0.4~0.8m.

3. The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages according to claim 1, characterized in that: The guide walls are symmetrically arranged on both sides of the top of the first-phase seepage barrier wall, and the width of each guide wall is 0.55~0.65m and the depth is 1m.

4. The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages according to claim 1, characterized in that: The second-phase seepage barrier wall is constructed from plastic concrete with a compressive strength of 1.5~2.5MPa.

5. The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages according to claim 1, characterized in that: The bottom surface of the second-stage cutoff wall is set at the same height as the bottom surface of the trapezoidal structure of the first-stage cutoff wall, and the width of the second-stage cutoff wall is equal to the sum of the widths of the first-stage cutoff wall and the guide wall.

6. The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages according to claim 1, characterized in that: The geogrid includes a type A geogrid installed above the secondary seepage barrier wall, a type B geogrid installed on the top surface of the dam soil, and a type C geogrid installed at the junction of the secondary seepage barrier wall and the top surface of the dam soil.

7. The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages according to claim 6, characterized in that: The A-type geogrid, the B-type geogrid, and the C-type geogrid have the same height, and the aperture size of the A-type geogrid is 25×25mm, the aperture size of the B-type geogrid is 50×50mm, and the aperture size of the C-type geogrid is 20×20mm.

8. The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages according to claim 1, characterized in that: Both the roadbed and the surface layer are sloped downwards at a 2% gradient along the direction of water flow.

9. The construction method for the crest of an earth-rock dam with a seepage barrier wall cast in stages according to claim 1, characterized in that: The surface layer comprises, from bottom to top, a 120mm thick 5% cement-stabilized crushed stone layer, a 6mm thick emulsified asphalt seal layer, a 50mm thick AC-16 dense-graded asphalt concrete mixture layer, and a 30mm thick AC-13 dense-graded asphalt concrete mixture layer.

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