Rainfall-induced shallow landslides, also called "soil slips", are becoming ever more frequent all over the world and are receiving a rising interest in consequence of the heavy damage they produce. At the University of Parma, a simplified physically based model has been recently set up for the evaluation of the safety factor of slopes which are potentially at risk of a soil slip. This model, based on the limit equilibrium method applied to an infinite slope, takes into account some simplified hypotheses on the water down-flow and defines a direct correlation between the safety factor of the slope and the rainfall depth. In this paper, this model is explained in detail and is used in a back analysis process to verify its capability to foresee the triggering instant of rainfall-induced shallow landslides for some recent case studies in the Emilia Romagna Apennines (Northern Italy). The results of the analyses and of the model implementation are finally shown.

A new experimental apparatus for performing impact tests is presented, to analyse the wave propagation phenomenon in pure sand and in composite sand-polyurethane specimens, with the final aim to explore the seismic mitigation given by a polyurethane inserted into a real soil under existing structures. Polyurethane layers at three different thicknesses are considered. Experimental results show that composite specimens provide acceleration reductions increasing with the increase of polyurethane thickness. Result interpretation in the light of the elastic wave propagation theory is presented, pointing out the experimental set-up limitations, mainly due to the lack of sufficient specimen confinement.

This paper analyses the effect of polyurethane injections on the seismic surficial response of cohesionless soils. For this purpose, dynamic finite element numerical analyses were performed through GiD + OpenSees. Both the soil and the composite material, resulted after the expansion of the injected polyurethane, are modelled with a nonlinear hysteretic constitutive model. Based on the polyurethane percentage, a homogenisation of the characteristics was considered for the composite material: linear for density and damping, and exponential (experimentally calibrated) for the stiffness. An expansion coefficient quantifies how much the injected polyurethane expands: three expansion coefficients were considered, each of them related to a different polyurethane density. For the evaluation of the foam stiffness, a linear stiffness–density correlation was used, derived after impact tests. Results showed that polyurethane reduces the surficial accelerations proportionally to the ratio of its seismic impedance and volumetric percentage with respect to the soil seismic impedance and total volume. This is a preliminary indication for the design of polyurethane injections in cohesionless soils for seismic acceleration reduction.

SLIP (Shallow Landslides Instability Prediction) is a mathematical model developed to foresee the triggering of rainfall-induced shallow landslides (soil slips) and the unstable condition of slopes affected by these phenomena. This physically-based model gives the factor of safety in function of the principal variables influencing the trigger of soil slips: rainfall, geometry, soil state, mechanical and hydraulic characteristics of soil. The specific characteristics of SLIP allowed to use the same means to model the phenomenon from the scale of the representative elementary volume (i.e. flume laboratory tests) to the medium and large scale (regional and national level). This paper (Part I), that is companion of another one published in this Conference (Part II), contains a brief description of the model and focuses on the approach followed in the application of the SLIP model at laboratory scale