El Zapotillo — A 130 metre-high RCC dam founded on a highly deformable rock mass

The El Zapotillo roller compacted concrete (RCC) dam, which is around 130 metres high, is being built on the Río Verde near Guadalajara, Mexico. The dam is built on highly deformable layers of tu‚, which are encountered in an alternating sequence with ignimbrite. Two layers of ignimbrite with a higher permeability form two artesian aquifers below the valley …oor. The design of the dam has to account for these di†cult ground conditions. The high deformability of the tu‚ layers in particular represents a major challenge in terms of proving stability. The design of the grouting and drainage concept is dominated by the two artesian aquifers. Proof of stability was provided with the help of 3D ‰nite element analyses using programme systems from the WBI consulting ‰rm. Construction of the dam and reservoir ‰lling and operation are and will be accompanied by an extensive monitoring programme and expert opinions in the sense of the so-called observational method, which is common in geotechnical engineering.