Face stability analysis of a shallow tunnel in the saturated and multilayered soils in short-term condition

An analytical model to predict the limit support pressure on a deep shield tunnel face

This study aims at the probabilistic assessment of tunnel convergence considering the spatial variability in rock mass properties. The method of interpolated autocorrelation combined with finite difference analysis is adopted to model the spatial variability of rock mass properties. An iterative procedure using the first-order reliability method (FORM) and response surface method (RSM) is employed to compute the reliability index and its corresponding design point. The results indicate that the spatial variability considerably affects the computed reliability index. The probability of failure could be noticeably overestimated in the case where the spatial variability is neglected. The vertical scale of fluctuation has a much higher effect on the probabilistic result with respect to the tunnel convergence than the horizontal scale of fluctuation. And the influence of different spacing of control points on the computational accuracy is investigated.

Probabilistic assessment of tunnel convergence considering spatial variability in rock mass properties using interpolated autocorrelation and response surface method

Undrained stability of a single circular tunnel in spatially variable soil subjected to surcharge loading

Reliability study on shield tunnel face using a random limit analysis method in multilayered soils

The stability condition of the tunnel face is of great importance in both conventional and modern [tunnel-boring machine (TBM)] methods of construction. Inadequate and excessive amounts of support pressure toward the face lead to surface settlement and blowout, respectively, whereas blowout occurs only in cases of pressurized shield implementation. In this research, the stability condition of a tunnel face excavated by an earth pressure balanced shield (EPBS) in Line 3 of the Tehran subway in Iran was investigated. Considering the sensitivity of urban facilities to ground movement, and to reduce uncertainty, data simulation by Monte Carlo technique was applied. Random data generated through a simulation process were used in an analytical method to calculate the factor of safety and its probability of being less than a predetermined value for a certain amount of applied support pressure. The soil was modeled by finite-element software, and the amount of face pressure at which the face collapses was...

Arash Eshraghi

Papers

Face Stability Evaluation of a TBM-Driven Tunnel in Heterogeneous Soil Using a Probabilistic Approach