The field of infrastructure rehabilitation and development requires a better understanding of soil-structure interactions. The interaction behaviour between soil and structures has mostly been investigated through theoretical and/or numerical analysis. This paper presents a series of experiments performed on an intermediate-scale physical model made of an instrumented silo. In contrast to most reported laboratory tests, both the horizontal and vertical stresses were monitored during backfilling operations realised by wild pouring. Drop tests were performed to investigate the density variation with respect to the drop (or falling) height of the soil, which were introduced in the pressure interpretation. The results showed that horizontal stress in the direction parallel to the pouring plane is larger than that perpendicular to the pouring plane. Apparently, the vertical stress is well-described using the arching solution by considering the backfill in an active state, whereas the horizontal stress perpendicular to the pouring plane is better described with the arching solution by considering the backfill in an at-rest state. An estimate of the earth pressure coefficients based on the measured vertical and horizontal stresses indicates, however, that the backfill was closer to an at-rest state in the direction perpendicular to the pouring plane, whereas in the direction parallel to the pouring plane, it was in a state between at-rest and passive. These results indicate that it is important to measure both the horizontal and vertical stresses to obtain a whole picture of the state of the backfill. The results showed also that the horizontal stresses can be larger than those calculated by the overburden solution, probably due to dynamic loading by drop mass during the filling operation and stress lock.
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