Implications of nonlinear shear strength and interface envelopes of reinforced compacted sand fills in very high earth structures

The adequate performance of geosynthetic reinforced structures depends to a great extent on the interface behavior between geosynthetic reinforcement and backfill. With some reported heights in the order of 50 meters or more, plus high surcharge loading, lower regions of these structures can experience high normal effective stress levels (≥ 1 MPa). The influence of high normal stress levels on the shear strength of sands is well documented, resulting in a curvilinear shear strength envelope due to decreased dilation and crushing at high stress levels. In contrast, the curvature of the effective interface shear strength for geosynthetic-granular backfill systems at high normal stress levels is not frequently reported in the literature; most interface friction studies report normal stress levels below 250 kPa and seldomly up to 500 kPa. The paper highlights this important knowledge gap and discusses possible implications of a curved interface shear strength envelope on the design and analyses of tall geosynthetic reinforced structures. The use of equivalent linear strength envelopes for subregions of the structure is described as a possible approach.