Effects of water content and particle crushing on the shear behaviour of an infilled-joint soil
Résumé
Ring shear tests were carried out on a compacted low plasticity infilled joint soil from Beihetan site. Different initial water contents (5.0, 9.0 and 13.5%) were considered. It was observed that the failure envelope is linear for the peak deviator stress but highly non-linear for the residual deviator stress in the range of high normal stresses (higher than 400 kPa), evidencing the particle crushing effect on the residual strength. Furthermore, this particle crushing effect was water content dependent: the residual friction angle is larger at higher water content. Further grain size analysis on the portion taken in the zone of shear band after each test was performed, and changes of the fractions of 75 µm and 2 µm were compared for different water contents. The results indicate clearly that the effect of water content on particle crushing depends on the particles size. For large particles (>75 µm), water content increase enhances the particle crushing by the fracture mechanism. On the contrary, for smaller particles (< 2 µm), water content increase reduces the particle crushing by the mechanism of attrition or abrasion. Deeper analysis of the effect of the ratio of the final to initial fraction of the particle size less than 2 µm, S2, on the shear strength suggests that the effect of particle crushing on the residual shear strength is mainly through the production of extra clay size particles (< 2 µm).