Avaliação de erosão interna em interfaces solo-concreto: estudo experimental e simulação de medida mitigadora

Abstract

Internal erosion is the transport of soil particles induced by percolation and is the main failure mode of embankment dams (46%). The carryover of soil particles can generate a greater risk of rupture when it interacts with adjacent structures, due to the great potential of preferential percolation paths along the interfaces. This greater vulnerability at the interface occurs due to the contrasting geotechnical properties between the soil mass and the adjacent structure, which can lead to the formation of unstable zones, tubes and cavities along the contact and, consequently, to rupture. Experimental studies and numerical simulations have been carried out to explore the phenomenon of internal interfacial erosion, but the models carried out do not take into account the contrasting properties at the soil-concrete interface. The objective of this work is, therefore, to analyze the water flow in soil-structure interfaces in order to evaluate the variable roughness of the structure in the soil permeability and to perform a three-dimensional computer simulation at the interface, considering the discontinuity in this region. The wall in embrace is also evaluated as a mitigating measure for the interfacial erosion process. The methodology consists of the development of an experimental model with different roughness and soil heights at 1 cm, 3 cm and 5 cm, in order to evaluate the influence of the roughness variable on the permeability of the soil mass. The modeling was carried out in three scenarios to simulate the interface of the spillway wall in a 200 m long earth dam. GEOSTUDIO's SEEP/W software was used to perform the simulations. The first scenario was carried out without an interface and without a embracing wall (dam massif), the second with an interface and without a embracing wall and the third with an interface and a 2 m long embracing wall. The experimental results revealed that the rougher the concrete surface, the lower the permeability of the soil-concrete interface system. The numerical simulation results showed that: (i) the soil-concrete interface is more vulnerable to water flows and that the dam massif (scenario 1-scenario 2); and (ii) the embracing wall provided the reduction of hydraulic gradients, proving to be an important measure to mitigate the risk of internal interfacial erosion (scenario 3). A compatibility between the results of the experiment and the simulations was also observed. It is concluded that the experiment-simulation approach is useful to assess the risk of internal erosion along soil-concrete interfaces.