Abstract: A series of stress path tests on typical soft soils (silt and organic silty clay) in the influence range of foundation pit in Fuzhou city were conducted by using triaxial apparatus with stress and strain control in order to research the stress-strain behaviours of unloading and loading caused by excavation and retaining structure of foundation pit. Compared with the results of triaxial tests between normal consolidation and K0 consolidation samples in the same confining pressure, it is indicated that there are large differences in deformation and strength. Based on the results of K0 consolidated triaxial tests, Duncan-Chang parameters were figured out and the methods of certification of each parameter in the model were put forward. At the same time, comparison with model parameters obtained by normal consolidation samples showed that some parameters had significant difference; and they decided the difference of stress-strain relationship. Duncan-Chang model parameters were suggested to obtained through triaxial loading and unloading test by K0 consolidation samples for the sake of satisfying numerical simulation analysis of foundation pit engineering. Duncan-Chang parameters of typical soft soils offered by the tests can be referred to numerical simulation of foundation pit engineering in Fuzhou city or other similar strata sites.

Key words: soft soil, stress path, stress-strain, K0 consolidation, Duncan-Chang model