An impervious structure for a roller compacted concrete dam and its construction method

Abstract

The present invention relates to a seepage prevention structure for a roller compacted concrete dam and its construction method, belonging to the field of water conservancy projects. The roller compacted concrete with rich cementitious materials of the second class is used below the dead water level elevation, and the roller compacted concrete with rich cementitious materials of the third class is used above it. The first and second copper water stops of the transverse joints of the dam are embedded in the roller compacted concrete with rich cementitious materials of the second class and the roller compacted concrete with rich cementitious materials of the third class. A copper water stop sheet is embedded at the concrete pouring surface of the dam body, and both ends of the copper water stop sheet are welded to the first copper water stop of the transverse joint of the dam. A polyurea coating is sprayed on the upstream surfaces of the roller compacted concrete with rich cementitious materials of the second class and the roller compacted concrete with rich cementitious materials of the third class. The advantages are as follows: above the dead water level elevation, the water head pressure is small, and the temperature difference between the concrete surface and the interior is large. By using the third-class concrete, the hydration heat can be effectively reduced, and the possibility of cracking on the upstream surface can be effectively reduced; below the dead water level elevation, the second-class concrete can play an effective seepage prevention role.

Description

Technical Field

[0001] The present invention belongs to the field of water conservancy projects, and particularly relates to an anti-seepage structure of a roller compacted concrete dam and a construction method thereof, which are applicable to roller compacted concrete dams such as concrete gravity dams and arch dams. Background Art

[0002] Roller compacted concrete dams are a new type of dam that emerged in the fierce competition between normal concrete dams and earth-rock dams. It combines the dual characteristics of the safe operation of concrete dams and the rapid construction of earth-rock dams, and has two major advantages of rapidity and economy. By the end of 2005, there were nearly 100 roller compacted concrete dams that had been built or were under construction in China, among which 23 had a dam height exceeding 100m. One of the representative "concrete core wall on rockfill" type roller compacted concrete dams (abbreviation: RCD), such as Tamagawa Dam in Japan, Shuikou Dam, Guanyinge Dam, and Baishi Dam in China. For the "concrete core wall on rockfill" type roller compacted concrete dam, roller compacted concrete is used for filling the inside of the dam body, and normal concrete (generally 2 - 3m thick) is used for anti-seepage and protection on the outside. The other is the full roller compacted concrete dam type (abbreviation: RCC), such as Puding Dam and Jiangya Dam in China. For the full roller compacted concrete dam, the entire cross-section of the dam body uses roller compacted concrete, and the roller compacted concrete itself is used for anti-seepage or only a thin anti-seepage layer is set on the upstream surface.

[0003] For the upstream anti-seepage surface layer concrete of roller compacted concrete dams, normal concrete and second-class aggregate rich mortar roller compacted concrete are mostly used, and copper water stops are set between the structural joints of different dam sections to meet the overall anti-seepage requirements of the dam. However, from the perspective of the existing concrete dams in operation, due to the hydration heat generated during the construction of mass concrete, under the action of temperature stress, the concrete on the upstream surface is extremely prone to cracking. At the same time, during the construction process, the pouring interval time of concrete on different placement surfaces is too long, and the pouring surface of roller compacted concrete has become a weak link in anti-seepage. Even some of the pouring surfaces will develop into deep or penetrating cracks, posing a great threat to the anti-seepage integrity and durability of the hydraulic structure. Summary of the Invention

[0004] The present invention provides an anti-seepage structure of a roller compacted concrete dam and a construction method thereof, which can effectively reduce the hydration heat of concrete during the construction process and enhance the anti-seepage ability of the upstream surface of the dam; it can effectively reduce the threat to the dam anti-seepage system caused by the surface cracks generated due to the long concrete pouring interval time.

[0005] The technical solution adopted by the present invention is as follows: below the dead water level elevation is the second-class aggregate rich-cementitious rolled concrete, and above the second-class aggregate rich-cementitious rolled concrete is the third-class aggregate rich-cementitious rolled concrete. The first copper waterstop and the second copper waterstop of the dam transverse joint are embedded in the second-class aggregate rich-cementitious rolled concrete and the third-class aggregate rich-cementitious rolled concrete. A copper waterstop sheet is embedded at the layer where the intermittent period of the dam body rolled concrete pouring is greater than 2 months or at the layer where the concrete is poured over the winter in cold regions, and both ends of the copper waterstop sheet are welded to the first copper waterstop of the dam transverse joint. A polyurea coating is sprayed on the upstream surface of the second-class aggregate rich-cementitious rolled concrete and the third-class aggregate rich-cementitious rolled concrete.

[0006] A construction method for the anti-seepage structure of a rolled concrete dam includes the following steps:

[0007] 1) Compaction of the upstream anti-seepage concrete: within a meters of the upstream water-facing surface of the dam body, a = 1 / 15h, where h is the water depth in front of the dam corresponding to the normal storage level. That is, the rolling direction of the second-class aggregate rich-cementitious rolled concrete and the third-class aggregate rich-cementitious rolled concrete should be parallel to the dam axis direction. The compaction thickness of the second-class aggregate rich-cementitious rolled concrete, the third-class aggregate rich-cementitious rolled concrete, and the dam body rolled concrete is 30 cm, and it is paved in one layer by leveling.

[0008] 2) The rolling operation adopts the strip lapping method. After the second-class aggregate rich-cementitious rolled concrete, the third-class aggregate rich-cementitious rolled concrete, and the dam body rolled concrete are leveled, a vibratory roller follows immediately for non-vibratory rolling for several passes. Then, several vibratory rollers perform parallel staggered rolling according to the required number of vibratory rolling passes. The rolling strips should be clear, and the deviation control is within 10 cm. The lap width between strips is not less than 20 cm, and the lap width at the end part is between 90 - 110 cm. For the convex strip formed between two rolling strips in the same rolling layer due to rolling operation, it is leveled by non-vibratory slow rolling for 1 - 2 passes; for the convex strip between two rolling strips on the placement surface, it is also leveled by non-vibratory slow rolling.

[0009] 3) Treatment of the concrete pouring layer: According to the dynamic construction progress arrangement, a copper waterstop sheet is pre-embedded in advance on the upstream side of the dam body at the layer where the intermittent period of concrete pouring is greater than 2 months or at the overwintering layer, and reliable protection measures are taken. Both ends of the copper waterstop sheet are welded to the side wings of the first copper waterstop of the dam transverse joint. Before pouring new concrete on this layer, it should be inspected. For defective parts such as cracking, loosening, and porosity, they should be chiseled and treated according to the requirements for treating concrete defects; for the remaining layers, the chiseling method is adopted. After each layer is treated and cleaned, and passed the acceptance, then the next bin of concrete is paved.

[0010] 4) The upstream concrete surface of the dam is polished and leveled. It is required that the base surface is flat, smooth, and has no sudden changes. After polishing, the base surface is cleaned by high-pressure air to remove the floating ash on the base surface, and it is required to be dry, clean, and free of dirt. Then, the polyurea coating is sprayed.

[0011] Precautions for spraying the polyurea coating in step 4): During the polyurea coating construction process, if strong winds and rain are encountered, construction must be stopped immediately and the polyurea coating must be covered with protective materials such as canvas. After the rain stops, wipe off the attachments on the polyurea coating.

[0012] The advantages of the present invention are: the anti-seepage structure of the rich-cement roller-compacted concrete + auxiliary anti-seepage layer is adopted, the head pressure is small above the dead water level, and in the water level fluctuation zone, the temperature difference between the concrete surface and the interior is large, and the three-graded concrete is adopted, which can effectively reduce the hydration heat and effectively reduce the possibility of cracking on the upstream surface; the two-graded concrete is adopted below the dead water level, which has excellent anti-seepage performance better than the two-graded concrete and can play an effective anti-seepage role; a layer of polyurea anti-seepage coating is sprayed on the upstream surface of the dam below the check flood level as an auxiliary anti-seepage layer, polyurea has good anti-seepage and low water absorption rate, can basically isolate water from penetrating into concrete and has excellent mechanical properties, can reduce or avoid the influence of fine cracks on the concrete surface on the anti-seepage of the dam, enhance the protection of the concrete and strengthen the anti-seepage of the dam body; the surface of the polyurea applied after the base surface is polished is smooth and flat, with good appearance, especially in severely cold areas, reduces the contact area between the outer coating and ice, and can effectively improve the ice pull-out resistance of the upstream surface of the dam. For layers where the concrete pouring interval is greater than 2 months or the wintering layer, water-stop copper sheets are pre-embedded on the upstream side of the dam body and reliable protection measures are taken. Welding the two ends of the waterstop with the first waterstop of the transverse joint can effectively reduce the threat posed by layer cracks caused by the long concrete pouring interval to the dam's anti-seepage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the present invention;

[0014] Figure 2 yes Figure 1 AA cross-section diagram. DETAILED DESCRIPTION

[0015] Below the dead water level is the second-level rich-cementitious roller-compacted concrete 1, and above the second-level rich-cementitious roller-compacted concrete 1 is the third-level rich-cementitious roller-compacted concrete 2. The first copper waterstop 3 of the dam transverse joint and the second copper waterstop 4 of the dam transverse joint are buried in the second-level rich-cementitious roller-compacted concrete 1 and the third-level rich-cementitious roller-compacted concrete 2. A waterstop copper sheet 7 is buried at the level where the pouring interval of the dam body roller-compacted concrete 8 is greater than 2 months or at the level 6 where the concrete is poured over the winter in severe cold areas, and both ends of the waterstop copper sheet 7 are welded to the first copper waterstop 3 of the dam transverse joint to ensure the penetration safety of the intermittent pouring level. Polyurea coating 5 is sprayed on the upstream surface of the second-level rich-cementitious roller-compacted concrete 1 and the third-level rich-cementitious roller-compacted concrete 2.

[0016] A construction method for a roller-compacted concrete dam anti-seepage structure comprises the following steps:

[0017] 1) Compaction of upstream anti-seepage concrete: Within a meters of the water-facing side of the dam body, a = 1 / 15h, where h is the water depth in front of the dam corresponding to the normal storage level. That is, for the second-grade aggregate-rich cementitious roller-compacted concrete 1 and the third-grade aggregate-rich cementitious roller-compacted concrete 2, the compaction direction should be parallel to the dam axis direction. The compacted thickness of the second-grade aggregate-rich cementitious roller-compacted concrete 1, the third-grade aggregate-rich cementitious roller-compacted concrete 2, and the dam body roller-compacted concrete 8 is 30 cm, and it is paved in one layer after leveling.

[0018] 2) The compaction operation adopts the strip lapping method. After the second-grade aggregate-rich cementitious roller-compacted concrete 1, the third-grade aggregate-rich cementitious roller-compacted concrete 2, and the dam body roller-compacted concrete 8 are leveled, a vibratory roller promptly follows for non-vibratory compaction twice. Then, several vibratory rollers perform parallel staggered compaction according to the required number of vibratory compaction passes. The compaction strips should be clear, and the deviation control is within 10 cm. The lap width between strips is not less than 20 cm, and the lap width at the end is between 90 - 110 cm. For the convex strip formed between two compaction strips in the same compaction layer due to compaction operation, it is leveled by non-vibratory slow compaction for 1 - 2 passes; for the convex strip between two compaction strips on the closing surface, it is also leveled by non-vibratory slow compaction.

[0019] 3) Treatment of the concrete pouring surface 6: According to the dynamic construction progress arrangement, if the concrete pouring interval is greater than 2 months or for the wintering surface 6 on the upstream side of the dam body, a water-stop copper sheet 7 is pre-embedded in advance and reliable protection measures are taken. The two ends of the water-stop copper sheet 7 are welded to the flanks of the first copper water-stop 3 of the dam transverse joint. Before pouring new concrete on the surface 6, inspections should be carried out. For defective parts such as cracking, loosening, and porosity, they should be chiseled and treated according to the requirements for treating concrete defects; for the remaining surface 6, the treatment method is scarifying. After the surface 6 treatment is completed and cleaned, and after passing the acceptance, the next bin of concrete is then paved.

[0020] 4) The upstream concrete surface of the dam is subjected to surface grinding and leveling treatment, requiring the base surface to be flat, smooth, and without sudden changes. After grinding, the base surface is cleaned with high-pressure air to remove the floating ash on the base surface, requiring it to be dry, clean, and free of dirt, and then the polyurea coating 5 is sprayed.

[0021] Precautions for spraying the polyurea coating 5 in step 4): During the construction of applying the polyurea, if strong winds and rain are encountered, the construction must be immediately stopped, and the polyurea coating 5 is covered and protected with protective materials such as canvas. After the rain stops, the attachments on the polyurea coating 5 are wiped clean.

[0022] The dust-proof structure of the present invention includes: 1) the anti-seepage structure of the dam body adopts rich cementitious roller compacted concrete + auxiliary anti-seepage layer + copper water-stop layer; 2) the rich cementitious roller compacted concrete is three-graded above the dead water level, using a high-admixture fly ash and low Vc value mix ratio, and two-graded below the dead water level. The total thickness of the rich cementitious roller compacted concrete is designed according to 1 / 15 of the normal water head in front of the dam; 3) in order to enhance the anti-seepage effect of the dam body, a layer of polyurea anti-seepage coating is sprayed on the upstream face of the dam below the verification flood level as an auxiliary anti-seepage layer; 4) according to the construction organization schedule, at the layer where the interval between roller compacted concrete pouring is greater than 2 months or the layer where concrete is poured over the winter in severe cold areas, a water-stop copper sheet is buried and welded to the first water-stop copper sheet of the dam transverse joint to form the anti-seepage structure of the dam.

[0023] The comparison of the effects of the present invention and conventional RCC dams is shown in Table 1.

[0024] Table 1 Comparison of the effects of the present invention and conventional RCC dams

[0025] heat of hydration seepage prevention property the present invention low high conventional roller-compacted concrete dam high low

[0026] It can be seen that the present invention can effectively reduce the hydration heat of concrete during the construction process and enhance the anti-seepage ability of the upstream surface of the dam.

Claims

1. A construction method for the anti-seepage structure of a roller compacted concrete dam, characterized in that, It includes the following steps: 1) Below the dead water level elevation on the upstream surface of the dam body is the second-class aggregate rich-cementitious content roller-compacted concrete, and above the second-class aggregate rich-cementitious content roller-compacted concrete is the third-class aggregate rich-cementitious content roller-compacted concrete. For the roller compaction of the upstream anti-seepage concrete: within a meters of the upstream water-facing surface of the dam body, a = 1 / 15h, where h is the water depth in front of the dam corresponding to the normal storage level. The roller compaction directions of the second-class aggregate rich-cementitious content roller-compacted concrete and the third-class aggregate rich-cementitious content roller-compacted concrete are parallel to the dam axis direction. The compacted thickness of the second-class aggregate rich-cementitious content roller-compacted concrete, the third-class aggregate rich-cementitious content roller-compacted concrete, and the dam body roller-compacted concrete is 30 cm, and it is paved in one layer of leveling. 2) The rolling operation adopts the strip lapping method. After the second-class aggregate rich-cementitious content roller-compacted concrete, the third-class aggregate rich-cementitious content roller-compacted concrete, and the dam body roller-compacted concrete are leveled, a vibrating roller immediately follows for non-vibrating rolling passes. Then, several vibrating rollers perform parallel offset rolling according to the required vibrating rolling passes. The rolling strips are clear, and the deviation is controlled within 10 cm. The lap width between strips is not less than 20 cm, and the lap width at the end part is between 90 - 110 cm. For the convex strip formed between two rolling strips in the same rolling layer due to the rolling operation, it is leveled by non-vibrating slow rolling for 1 - 2 passes; for the convex strip between two rolling strips on the pouring surface, it is also leveled by non-vibrating slow rolling. 3) Treatment of the concrete pouring surface: According to the dynamic construction progress arrangement, if the concrete pouring interval is more than 2 months or for the wintering surface, a water-stop copper sheet is pre-buried on the upstream side of the dam body and reliable protection measures are taken. The two ends of the water-stop copper sheet are welded to the first copper water-stop flank of the dam transverse joint. Before pouring new concrete on this surface, inspections are carried out, and for the defective parts such as cracking, loosening, and porosity, they are chiseled and treated according to the requirements for concrete defect treatment; for the treatment of the remaining surfaces, the chiseling method is adopted. After each surface treatment is completed and cleaned, and after passing the acceptance, the next bin of concrete is then paved. 4) The upstream concrete surface of the dam is subjected to surface grinding and leveling treatment, requiring the base surface to be flat, smooth, and without sudden changes. After grinding, the base surface is cleaned by high-pressure air to remove the floating ash on the base surface, requiring it to be dry, clean, and free of dirt, and then the polyurea coating is sprayed.

2. The construction method of an impervious structure for a roller-compacted concrete dam according to claim 1, characterized in that: Precautions for polyurea coating spraying in step 4): During the construction of polyurea coating brushing, if strong winds and rain are encountered, construction must be immediately stopped, and the polyurea coating is covered and protected with canvas protective materials. After the rain stops, the attachments on the polyurea coating are wiped clean.

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