One-dimensional self-weight consolidation approach to evaluate internal bleeding in concrete during its implementation in diaphragm wall

Abstract Diaphragm walls are deep reinforced concrete structures cast into the ground allowing the construction of numerous works located in very varied sites and geotechnical conditions (underground station, parking lot, etc.). The pressure applied by the self-weight of the fresh concrete placed inside the deep excavation entails excessive internal bleeding. Significant defects like chimneys of water upwelling (channeling) appears on the wall siding despite the use of filtration test apparatus developed to detect tendencies of concrete bleeding under pressure. This paper proposed an approach from the one-dimensional self-weight consolidation theory, based on soil mechanics, to assess the evolution of the hydrostatic pore pressure in the concrete during its implementation in a diaphragm wall. The investigated concrete was proportioned with a cement water ratio (w/c) of 0.49 to 0.55 with different fines content. A case study is discussed from a concrete poured on site which presented channeling was studied. The experimental results showed that the concrete water migration can start during the pouring phase what was observed on an instrumented column of 1.5 m high. The simulation results from concrete oedometer tests and columns indicates that the consolidation coefficient of concrete is a good indicator of the risk of the appearance of bleed channel.