Effect of strain rate on the adhesive bond shearing resistance of stiff clay

Up to now, the effect of strain rate on the adhesive bond shearing resistance of stiff clay, which plays a fundamental role in constitutive modeling of such kind of soils, remains unclear. This paper aims to experimentally investigate the strain rate dependency of the adhesive bond shearing resistance of stiff clay. Both undisturbed and reconstituted overconsolidated samples of Merville stiff clay from the Flanders region in the north of France are prepared with different overconsolidation ratios (OCR, up to 56). Oedometer tests and undrained triaxial tests under different confining stresses on samples with different OCRs are conducted. The effect of inter-particle bond is gradually investigated by comparing test results of undisturbed and reconstituted samples with the same OCR. All results suggest a uniqueness of the strain rate dependency in one-dimensional and triaxial conditions with different OCRs for the reconstituted clay, whereas the strain rate dependency of shear strength of overconsolidated clay is found to be higher in undisturbed samples than in reconstituted samples due to inter-particle bonding. This new finding is formulated as the adhesive bond shearing resistance against the strain rate, which should be useful for improving the time-dependent modeling of highly overconsolidated stiff clays.