Yielding of Rockfill under Relative Humidity Control

Abstract

Although rockfill materials are widely used in geotechnical engineering, some aspects of their behavior, with respect to the influence of suction, still raise some questions. This research is an investigation of the effect of total suction on the yielding of rockfill during triaxial compression tests, with a focus on quantifying its influence on key mechanical properties. The difficulty of testing rockfill, owing to its dimensions, together with the scarcity of data in the literature on the effect of suction, increases the importance of this work. To address this gap, triaxial compression tests were conducted on rockfill specimens under controlled relative humidity conditions (50%, 75%, and 100%), which are directly related to total suction (93.86, 38.95, and 0 MPa). In the tests, particle breakage evolution was assessed using the Einav breakage index. Dilatancy behavior showed a very limited influence of total suction and was analyzed, considering, for what is understood to be the first time, the relationship between stress ratio, particle breakage, and mean confining stress. At the end of the tests, dilatancy was found to be practically independent of suction, decreasing only with confining stress to 1/3 (for the studied confining stresses: 0.20, 0.40, and 0.75 MPa). The peak failure envelopes were fitted to exponential equations, and the parameters of these equations were evaluated as a function of relative humidity, thus enabling the influence of this variable to be determined. The experimental results reveal that the main effect of decreasing the total suction (or increasing the relative humidity) is contraction of the peak failure envelopes in the