Probabilistic analysis of ground settlement induced by soil and rock composite foundation excavation considering spatial variability

The deposition processes of geotechnical materials are inherently complex, resulting in significant spatial variability in soil and rock properties. This study proposes a probabilistic framework applicable to braced excavations in composite soil-rock layers, designed to quantitatively evaluate the impact of variability on these excavations and to explore its potential implications. The framework integrates Latin Hypercube Sampling, Monte Carlo, and finite difference methods. The foundation pit excavation for Qilu Hospital serves as a case study to illustrate the approach, beginning with a deterministic assessment to investigate ground settlement behavior in a composite soil-rock environment. Subsequently, the study evaluates the influence of two critical factors on surface settlement: the scale of fluctuation in random fields and Young's modulus's coefficient of variation (COV). The deterministic analysis provides insight into ground settlement mechanisms in composite soil-rock conditions. In contrast, the probabilistic analysis, which incorporates random fields, demonstrates that spatial variability exerts a considerable influence on both ground settlement and the stability of the foundation pit. In particular, an increase in the scale of fluctuation affects the range of settlement values, while variations in the COV have a significant impact on the probability of failure and the distribution of settlement outcomes within the foundation pit.