Criteria for the design of embankment dams founded on gypsiferous geological formations

Abstract

This article sets criteria for selecting the typology of embankment dam and the elements for the foundation to be impervious enough (blanket, cutoff…) when the dam site contains disseminated gypsum particles in limited quantities (less than 40%) and the flow is interstitial. Numerical modeling analysis of the soluble material dissolution of a dam foundation includes two coupled processes: seepage and dissolution. In a previous manuscript, the mathematical model that simulates the progress of the dissolution of the gypsum particles in the foundation was implemented in the code DISOLUCION2D, also validated by experimental work. This code simulates the advance of the dissolution front (foundation area where the dissolution of soluble particles is taking place) at each time step, based on the flow velocities obtained from the seepage flow net calculation. The dissolution process progressively increases the permeability of the foundation and therefore the flow rate under the dam, jeopardising in some cases the safety of the dam. Based on the validated code, a study covering 140 cases of dams and their foundations was carried out. From the relevant data for each dam site (height, thickness of the gypsiferous layer, gypsum percentage of the layer) and the prescribed criteria for maximum permissible flow rate or maximum flow rate increase, the various type sections of the dam that satisfy the required conditions can be identified. From among these, the dam designer will be able to choose the optimal solution, taking into consideration the particular characteristics of the project (available materials, economic costs...).