Incorporating Rainfall Forecast Data in X-SLIP Platform to Predict the Triggering of Rainfall-Induced Shallow Landslides in Real Time

Extreme and prolonged rainfall resulting from global warming determines a growing need for reliable Landslide Early Warning Systems (LEWS) to manage the risk of rainfall-induced shallow landslides (also called soil slips). Regional LEWS are typically based on data-driven methods because of their greater computational effectiveness, which is greater than the ones of physically based models (PBMs); however, the latter reproduces the physical mechanism of the modelled phenomena, and their modelling is more accurate. The purpose of this research is to investigate the prediction quality of the simplified PBM SLIP (implemented in the X-SLIP platform) when applied on a regional scale by analysing the stability of rain forecasts. X-SLIP was updated to handle the GRIB files (format for weather forecast). Four real-time predictions were simulated on some towns of the Emilia Apennines (northern Italy) involved in widespread soil slips on 5 April 2013; specifically, maps of factors of safety related to this event were derived assuming that X-SLIP had run 72 h, 48 h, 24 h and 12 h in advance. The results indicated that the predictions with forecasts (depending on the forecast quality) are as accurate as the ones derived with rainfall recordings only (benchmark). Moreover, the proposed method provides a reduced number of false alarms when no landslide was reported to occur in the whole area. X-SLIP with rain forecasts can, therefore, represent an important tool to predict the occurrence of future soil slips at a regional scale

Analysis of the Behaviour of Very Slender Piles: Focus on the Ultimate Load

AbstractThe paper aims to analyse the influence of slenderness on the ultimate behaviour of piles with a very small diameter (less than 10 cm) that are often employed in soil reinforcement and for which the slenderness can significatively influence the failure behaviour, reducing the ultimate load. The aim is reached by means of numerical analyses on small-diameter piles of different geometries, embedded in clayey soil. The critical load is evaluated numerically in undrained conditions and then compared to the bearing capacity estimated by the classical approaches based on limit equilibrium method. The numerical model is first calibrated on the basis of the results of experimental laboratory tests on bored piles of a small diameter in a cohesive soft soil (average undrained shear strength cu = 15 kPa). The comparison between the critical load and the bearing capacity shows that their ratio becomes less than 1 for critical slenderness LCR that decreases, nonlinearly, with the decreasing of the pile diameter. The results of the analysis show that varying the diameter of the pile from 0.06 to 0.18 m, LCR varies from 65 to 200. The aforementioned evidence suggests that the evaluation of the ultimate load of piles of very small diameter has to follow the considerations on the critical load of the pile, especially if it is embedded in soft soil; on the contrary for piles of greater diameters (bigger than 20 cm) the buckling is not meaningful because LCR is so big that the common slenderness does not exceed it

Rainfall-induced shallow landslides triggered after vegetation removed because of fires: G-XSLIP application to Gioiosa Marea (Sicily, Italy)

The paper analyses how vegetation prevents the triggering of rainfall-induced shallow landslides by using the G-XSLIP platform, which is based on G-SLIP model, i.e., the SLIP model updated with vegetation parameters for root reinforcement and rain interception due to canopy. G-XSLIP is applied to an area in Gioiosa Marea (Sicily, Italy), where on 9th September 2016 shallow landslides occurred, depositing on the state road SS 113. The analyses demonstrate that the triggering of these phenomena is related to the removal of vegetation after summer fires some months before, which decreases computed safety factors by about half

Analisi sperimentale e teorica della mitigazione del rischio sismico attraverso interventi nel terreno con materiali sintetici

The PhD thesis has been finalized to study the influence of synthetic materials on propagation of waves coming from earthquakes; since soil modifies seismic waves in terms of maximum acceleration and frequency content, how underground inclusions affect the propagation has been focused by the work. Materials analyzed have been polyurethanes, i.e. cellular polymers widely applied in different fields; from a geotechnical point of view, they are mainly used for settlement reduction or consolidation of foundation soils. Polyurethanes have been first studied under static and cyclic loads, by performing oedometric, triaxial and resonant column tests, in order to analyze their behavior for geotechnical tensional states. The thesis aim has been focused after the realization of an experimental system for unidimensional wave propagation studies, consisting of a containing box, where impact hammer tests have been performed. The experimental set-up has been theoretically and numerically calibrated on sandy specimens; composite specimens have been then realized. Polyurethane has been included in slab form, showing reductions of recorded accelerations increasing with width, for such impacts that accelerometer stability is guaranteed. For higher energy impacts, the experimental system has shown its limits, confirmed by theoretical modeling. Inspired to Deep Injection technology, polyurethane has been injected in soil, by means of syringes; however, this solution does not allow to realize in-pressure injections, typical in soil intervention techniques. A numerical model, calibrated on the experimental results, has allowed to numerically deepen the experimental campaign, analyzing further aspects, difficult to be experimentally investigated because of practical efforts and limits

Experimental Analyses on Cellular Polymers for Geotechnical Applications

Cellular polymers represent an important category within the area of the polymeric materials. Although these materials are experiencing a growing importance from both an industrial and an economic point of view, there is not such a big and detailed corresponding scientific literature. Except for the researches directly supported by the manufacturing companies, mainly interested, there are only few scientific and engineering studies about this argument. This article is aimed to the geotechnical characterisation of the rigid polyurethane foam and the extruded polystyrene foam and their physical- mechanical properties. The mechanical behaviour is investigated through oedometric and triaxial tests, performed in either PUR and XPS samples at different densities. As a result, the influence of the density on the relationship stress-strain for the materials is obtained. Practical methods and procedures about how to adapt the geotechnical tests on such materials, different from the soil, are also illustrated. At the end of the analyses, a first attempt of interpretation is given, so that an analytical model for the geotechnical description of cellular polymers can be developed

Experimental analyses on cellular polymers in different forms for geotechnical applications

Cellular polymers represent an important category among the polymeric materials. Nowadays they experience large applications in different areas (packaging, building, sport, road safety). There is already a widespread geotechnical use of these materials, e.g. for settlements reduction or soil strengthening, especially for existing structures. However, a need of a deeper mechanical properties study is required. Oedometric and triaxial laboratory tests have already been carried out on polyurethane samples obtained from ready-to-be-used slabs (RTBU samples). However, because of a will of polyurethane foam injection inside the soil, an ad-hocprepared foam needs to be prepared and its mechanical properties to be investigated. This paper is therefore aimed to analyse the geotechnical behaviour of the ad-hoc-prepared foam (by testing AHP samples), studying the influence of several factors on the applicability, and comparing the results with the failure tests conducted on RTBU samples

WAVE PROPAGATION IN SANDY SOIL – AN EXPERIMENTAL AND NUMERICAL MODEL

Existing seismic retrofitting techniques are mainly structural and invasive. Since earthquakes generates from soil and seismic waves propagate through it, alternative solutions for seismic retrofitting have been thought, concerning the insertion of innovative materials in the soil. Polyurethane materials (such as Styrodur or ElastoPor) have already been widely investigated by laboratory testing. In order to evaluate the benefit of their insertion in the soil in terms of PGA decrease and frequency content modification, a little-scale wave propagation study is now introduced. Controlled impact hammer tests adapted to geotechnical uses are performed in a small test wood caisson filled with sand. A FEM model is therefore presented and calibrated on the basis of the comparison with the experimental results. A good agreement between experimental and numerical results allows to anticipate future numerical application of the model to larger studies finalised to the evaluation of seismic amelioration due to polyurethane insertion

On the Use of MATLAB to Import and Manipulate Geographic Data: A Tool for Landslide Susceptibility Assessment

Most of the methods for landslide susceptibility assessment are based on mathematical relationships established between factors responsible for the triggering of the phenomenon, named the conditioning factors. These are usually derived from geographic data commonly handled through Geographical Information System (GIS) technology. According to the adopted methodology, after an initial phase conducted on the GIS platform, data need to be transferred to specific software, e.g., MATLAB, for analysis and elaboration. GIS-based risk management platforms are thus sometimes hybrid, requiring relatively complex adaptive procedures before exchanging data among different environments. This paper describes how MATLAB can be used to derive the most common landslide conditioning factors, by managing the geographic data in their typical formats: raster, vector or point data. Specifically, it is discussed how to build matrices of parameters, needed to assess susceptibility, by using grid cell mapping units, and mapping them bypassing GIS. An application of these preliminary operations to a study area affected by shallow landslides in the past is shown; results show how geodata can be managed as easily as in GIS, as well as being displayed in a fashionable way too. Moreover, it is discussed how raster resolution affects the processing time. The paper sets the future development of MATLAB as a fully implemented platform for landslide susceptibility, based on any available methods

The role of plants in the prevention of soil-slip: the G-SLIP model and its application on territorial scale through G-XSLIP platform

This paper discusses the role of plants in the prevention of shallow landslides induced by rain (soil slips); these phenomena, related to “hydrogeological instability”, are among the most feared because their evolutionary processes can cause huge damages and losses of human lives when interacting with anthropized areas and infrastructures. The paper first highlights how the plants interact with the soil; then introduces the G-SLIP (Green - Shallow Landslides Instability Prediction) model, i.e. the simplified physically-based SLIP model, modified to predict soil slips at punctual and large scale taking into account the vegetation effects. G-SLIP model is thus applied to a case study of the Parma Apennines (Northern Italy) by using the G-XSLIP platform. In this area, during the intense events of rain between the 4th and 5th of April 2013, numerous landslides occurred, provoking huge damages to structures and infrastructures, and consequent economic losses. The stability analyses carried out with G-XSLIP demonstrate that the presence of vegetation in the study area led to a significant reduction in the triggering of shallow landslides. Finally, an attempt of soil slip mitigation through naturalistic techniques (planting of specific vegetation) is presented

Rainfall-induced shallow landslides triggered after vegetation removed because of fires: G-XSLIP application to Gioiosa Marea (Sicily, Italy)

The paper analyses how vegetation prevents the triggering of rainfall-induced shallow landslides by using the G-XSLIP platform, which is based on G-SLIP model, i.e., the SLIP model updated with vegetation parameters for root reinforcement and rain interception due to canopy. G-XSLIP is applied to an area in Gioiosa Marea (Sicily, Italy), where on 9th September 2016 shallow landslides occurred, depositing on the state road SS 113. The analyses demonstrate that the triggering of these phenomena is related to the removal of vegetation after summer fires some months before, which decreases computed safety factors by about half