Numerical Analyses of an Excavation Case in Thick Soft Clay with the Aid of SCPTU Test

The HSS model is often used for excavation analysis because of its excellent performance in modeling the small strain behavior of soil. The reliability of the numerical analysis using the HSS model depends on high-quality soil parameters. However, obtaining undisturbed samples for sands, silts, and muddy clay is difficult. This paper presented a numerical simulation of a subway station excavation located in the Yangtze River floodplain area of Nanjing. The subway station is surrounded by thick soft clay, and it is difficult to obtain high-quality samples. A SCPTU-based method was proposed to determine the HSS model parameters of soft clay. Since the SCPTU test is conducted in the in situ stress state, it overcomes the problems of sampling disturbance. The soil parameters obtained by the SCPTU test were used to calculate the excavation-induced lateral wall movements through numerical analysis. The numerical analysis results were compared with the measured values, and those obtained by numerical analysis which the soil parameters were calculated by soil compression modulus. It was found that, after excavation, the numerical simulation results based on the SCPTU test are consistent with the measured values. However, the simulated maximum lateral wall movement is only 53% of the measured value. The SCPTU-based parameters are more reliable than those based on soil compression modulus.