Effects of thixotropy and reconsolidation on the undrained shear characteristics of remoulded marine clays

The undrained shear properties of remoulded clay are important in the design of offshore infrastructure. The effects of thixotropy and reconsolidation on the undrained shear strength and shear modulus of remoulded marine clays were investigated by direct simple shear and bender element tests. The results show that both the shear strength and shear modulus of the remoulded clays after reconsolidation are independent of the thixotropic hardening time after remoulding. This indicates that the effects of thixotropy and reconsolidation on strength gain of remoulded clays are not additive. Compared with the intact samples, both the ratio between undrained shear strength and in situ effective pressure (suD/cv0') and the ratio between shear modulus and in situ effective pressure (Gmax/cv0') on the reconsolidated remoulded samples are much lower for the soils tested herein with over-consolidated ratio (OCR) about 2 and higher, while the rigidity index (Gmax/suD) is similar between remoulded and intact clays. The ratio between reconsolidated remoulded strength and intact strength (suD,rr/suD, intact) is dependent on the OCR of the intact soil, and decreases with increasing OCR. The ratio between the reconsolidated remoulded shear strength and the applied reconsolidated stress (suD,rr/cvc') increases with decreasing reconsolidation stress, and is also related to OCR.