Plastic concrete cut-off walls in earth dams
US Army Corps of Engineers.
“This research was conducted to quantify the stress-strain-strength behavior and permeability of plastic concrete, and to develop design data for specifying plastic concrete for use in a diaphragm cutoff wall for an earth dam…”.
Deformation and Hydraulic Conductivity of Cement-Bentonite Slurry Cut-Off Walls
Nuha Jamal Alzayani.
“Cement-Bentonite slurry cut-off walls are low permeability vertical barriers that are used for cutting-off water flow in engineering groundwater facilities such as dams and
levees, or containing waterborne contaminants in waste treatment systems…”.
“Coquitlam Dam, constructed in the early 1910s, is a 30 m high hydraulic fill embankment. The dam is situated in a region of high seismic hazard in British Columbia, Canada. The existing dam core and shells, and part of the dam foundation are deemed to be liquefiable under the design earthquake. A new 30 m high compacted earth core rockfill embankment dam is currently being constructed at the downstream toe of the existing dam. As part of the construction of the new dam, a seepage cutoff wall has been completed underneath the central core of the new embankment to control foundation seepage gradients and to minimize piping potential of the foundation soils. The wall was constructed of plastic concrete using slurry panel construction method. Plastic concrete was selected to provide a seepage cutoff wall that has sufficient strength to withstand both static and seismic stresses beneath the new embankment, and yet is flexible enough to undergo seismic deformations, without cracking, with the surrounding soils. This paper describes the construction of the plastic concrete cutoff wall for the new Coquitlam dam, including the field and laboratory testing performed to confirm design wall stiffness, strength, and hydraulic conductivity requirements. The trial laboratory and field testing programs to determine plastic concrete mix design, and the QA/QC testing conducted during construction, including measurement of in-situ hydraulic conductivity of the constructed plastic concrete panels, are presented…”.
Design and construction of deep secant pile seepage cut-off walls
Peter D Amos et al.
“Arapuni Dam was completed in 1927 and is a 64m high curved concrete gravity structure across the Waikato River in New Zealand. A series of foundation leakage events related to piping and erosion of clay infill within joints in the rock foundation have occurred since the dam was built. Leakage was evidenced by increased drainage flows and uplift pressures. The paper describes the design and construction features of the deep seepage cutoff walls that have recently been completed to control piping and erosion in the foundation…”.
The world’s largest cutoff Wall at Karkheh dam
A.A. Mirghasemi et al.
“Plastic concrete cutoff walls have been used forsome three decades following the developmentof various techniques for constructing underground diaphragms, which can be convenient and economical. Diaphragm walls are generally excavated in panels, with the excavated area supported by bentonite slurry. The first reported application of plastic concrete was for the cutoff of the Santa Luce dam in Italy in 1959 [Xanthakos, et al., 19941]. This cutoff was 354 m long, 1.2 m thick and had maximum depth of 20 m. The foundation watertightness at the Karkeh dam is mostly achieved by a cutoff wall. The characteristics of the material (plastic concrete) were designed in such a way as to ensure the required impermeability, deformability and strength. At present, the wall surface area is about 190 000 m2. The depth of the wall in its deepest section is about 80 m, while the average depth is about 50 m. The thickness of the wall is a function of the depth, and was selected to be either 100 or 80 cm…”.