Analysis of shallow failures triggered by the 14-16 November 2002 event in the Albaredo valley, Valtellina (Northern Italy)

摘要

On 14-16 November 2002 the North Italy was affected by anintense rainfall event: in the Albaredo valley (Valtellina) more than 200 mmof rain fell triggering about 50 shallow landslides, mainly soil slips andsoil slip-debris flows.

Landslides occurred above the critical rainfall thresholds computed byCancelli and Nova (1985) and Ceriani et al. (1994) for the Italian CentralAlps: in fact the cumulative precipitation at the soil slips initiation timewas 230 mm (in two days) with a peak intensity of 15 mm/h.

A coupled analysis of seepage and instability mechanisms is performed inorder to evaluate the potential for slope failure during the event. Changesin positive and negative pore water pressures during the event are modelledby a finite element analysis of water flow in transient conditions, using asboundary condition for the nodes along the slope surface the recordedrainfall rate. The slope stability analysis is conducted applying the limitequilibrium method, using pore water pressure distributions obtained in thedifferent time steps by the seepage analysis as input data for thecalculation of the factor of safety.