Dilatancy based calculation of lateral earth thrust and the locked-in stress concept

Precise calculation of the loads and stresses that are acting on structures that are interacting with soils is central to the design of geotechnical structures. Accordingly, calculation of vertical soil stresses is a straightforward task whereas computation of lateral stresses is a topic of ongoing research. Conventional design methods for retaining structures consider the ultimate lateral earth pressures, namely active and passive earth pressures. As it is clearly identified in geotechnical literature, strength of backfills and the shapes of the failures planes control the magnitudes of active and passive thrust on retaining structures. Accordingly, this study attempts to come up with a precise method for the calculation of active and passive earth thrusts. For this purpose, a new equation (Altunbaş 2014) that uses dilatancy angle for the calculation of the geometry of the active failure plane is incorporated into the method of slices for the computation of active earth thrust. Accuracy of the proposed method is checked using the results obtained from small-scale physical retaining wall model tests. The same approach is repeated for passive earth thrust. Differences between the computed and measured results are discussed and the reasons for the differences are discussed theoretically. A new concept called locked-in stresses is developed to consider elastically stored residual normal stresses in soil bodies and their influences strength.