| Dams
several key components, including a concrete face with vertical joints, transition zones on the upstream side, external plinth, external grouting, as well as various types of water stops and mastics. For ACRDs, the sealing system comprises an asphalt wall that runs along the dam’s length. This system also incorporates fine and coarse transition zones, an internal plinth, internal grouting, and an asphalt core positioned in the center of the dam.
Design sections – Zoning Typical cross sections and zoning for CFRDs and
ACRDs are indicated as shown on Figures 4 and 5.
Transition Zones Fine and coarse transition zones are significant construction elements in both CFRDs and ACRDs, and their respective sequences are illustrated in Figures 6 and 7.
In CFRDs, the inclusion of an extruded concrete curb is necessary, particularly in front of zone 2B (as depicted in Figure 6). Meanwhile, in ACRDs, transition zones are positioned both upstream and downstream of the asphalt core (as shown in Figure 7). These transition components are installed concurrently with the advancement of the asphalt core.
Foundation Treatments - grouting strategies
In both CFRDs and ACRDs, foundation treatments hold paramount significance in terms of permeability control and leakage prevention. The management of foundation permeability through cement grouting is a standard practice and follows a well-established pattern in both alternatives. A notable method known as the GIN method, as proposed by Lombardi and Deere in 1993, has been widely employed in some of the tallest CFRDs worldwide, such as Aguamilpa in Mexico and Mazar in Ecuador. For instance, Figure 8 illustrates the grouting
treatment employed at the Tianshengqiao.1 Dam in China, which stands at an impressive height of 178m. In this case, the grouting is administered on the plinth, which is situated over the external rock foundation, on the outside of the compacted rockfill. Conversely, Figure 9 showcases the Storglomvatn Dam, where a typical grouting treatment is carried out from the plinth situated at the central core abutment of the dam in the case of ACRD.
Construction phases In the case of ACRDs, the initial construction stage
involves the early development of the concrete plinth at the central part, conducted alongside the foundational grouting services. Additionally, the treatment of the foundation rock surface follows established international rock standards and necessitates meticulous cleaning with compressed air. Prior to proceeding further, a crucial step involves the application of pre-coating material (primer) to facilitate strong adhesion between the asphalt core and the concrete surface of the plinth. The commencement of the asphalt core construction follows these preparatory measures. It’s imperative to note that all these activities are considered critical components in the primary construction sequence for a rockfill dam of this nature.
1A 1B 3B 3D
In the CFRD alternative, the foundational treatment,
concrete pouring, and grouting services occur upstream of the primary dam. Significantly, these activities can be carried out with a relatively high degree of independence from the progress of the primary rockfill construction.
Above: Figure 3: Storglomvatn dam ( near completion) ACRD, 125m high, Norway. Vahid A., Dam World Conference, Lisbon, Portugal, 2015
2A
2B 3A
PLAN 3A
Large rock dozed to face
3C 2
Face Slab
Angle depends on height of dam, rock quality
1A Impervious Soil 1B Random – 0.5m Layers
2 Processed small rock Transition
3A Selected small rock placed in same layer thickness as Zone 2
3B about 1m Layers
3C about 2.0m Layers
3D
Compaction for rock zones 4 passes of 10 ton VIB. Roller
Figure 4: Typical CFRD cross section of sound rock on sound rock foundation (Barry Cooke, 1993, China; 2nd Symposium on CFRD, Brazil 1999)
275 270 265 260 255 250 245 240 235 230 225 220 215 210
WL RESERVOIR COFFERDAM AXIS PRE-COFFERDAM 4 Topo 7 Rochoso
1) Asphalt Core 2) Fine Transition 3) Coarse Transition 4) 5) 6) 7) Plinth
Figure 5: Foz do Chapecó cross section ACRD, BRAZIL on sound rock foundation (Bayardo, M., CHINCOLD 2013, 3rd Internat. Symposium on Rockfill Dams, Kunming, China)
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2 3
2 3
4 1 5 COFFERDAM AXIS PRE-COFFERDAM 6 DOWNSTREAM
Plinth
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