ABSTRACT
Deterministic face support pressure analyses neglects incorporating geological-geotechnical spatial uncertainty. The simplified reliability-based design adopted previously account for uncertainty in the geotechnical parameter space by means of random variables but fail to capture the soil spatial variability. This paper investigates the impact of soil variability on face stability for a large diameter tunnel in soft ground. The analytical models suggested by Hong Kong Geo-Tunnelling guidance and TU Delft are used to model the collapse and blowout pressure, respectively. Soil variability is modeled with stochastic geostatistical methodologies to capture complex soil heterogeneities. A comparative assessment of the influence of soil variability and geotechnical parameters on support pressures is presented. Capturing uncertainty in soil types indicate a possible reduction in the TBM operational range. It is believed that this study provides a practical and reliable framework for determining the stability of tunnels in complex soil strata.
