Speaker
Description
Ground surface settlement is a common phenomenon in urban tunneling through layered soil–rock systems, particularly where bedrock faults intersect the tunnel and connect to overlying soils. This study employs a fully coupled hydro‑mechanical finite element model to quantify how stratigraphy and fault properties jointly govern the magnitude, spatial distribution, and temporal evolution of settlement in a composite profile comprising an overconsolidated clay layer, a thin permeable frictional layer, and faulted crystalline bedrock. The simulations explore two configurations (with and without a frictional layer), a wide range of fault permeabilities and dip angles, and time scales from 1 day to 10 years. Results indicate that the presence of a thin, highly conductive frictional layer amplifies long‑term surface settlement by approximately threefold and produces wider, flatter settlement troughs compared with a simple clay–bedrock system. For highly permeable faults (with fault permeability kf ~10-6 to 10-12 m2), the settlement profile is strongly affected by the fault's position, with the maximum settlement shifting from above the tunnel axis toward the projection of the fault intersection at the soil–rock interface, whereas low-permeability faults (with kf < 10-12 m2) have limited influence and keep the maximum settlement above the tunnel. The thickness of the frictional layer also plays an important role in ground settlement, contributing to increased settlement magnitudes. These findings provide useful insights for developing tunneling strategies, especially in urban areas encountering composite soil-rock ground conditions, and for improving the safety assessment and the planning of future tunneling projects.
| Country | Sweden |
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