Valentina Lentini

One-dimensional Seismic Analysis of a Solid-Waste Landfill

Analysis of the seismic performance of solid waste landfill follows generally the same procedures for the design of embankment dams, even if the methods and safety requirements should be different. The characterization of waste properties for seismic design is difficult due the heterogeneity of the material, requiring the procurement of large samples. The dynamic characteristics of solid waste materials play an important role on the seismic response of landfill, and it also is important to assess the dynamic shear strengths of liner materials due the effect of inertial forces in the refuse mass. In the paper the numerical results of a dynamic analysis are reported and analysed to determine the reliability of the common practice of using 1D analysis to evaluate the seismic response of a municipal solid‐waste landfill. Numerical results indicate that the seismic response of a landfill can vary significantly due to reasonable variations of waste properties, fill heights, site conditions, and design rock motions.

Landsliding Events Triggered by Rainfalls in the Enna Area (South Italy)

The factors affecting slope stability are various, and virtually most are closely interconnected. Among these, meteoric events (or rather, the effects induced by these) are of primary importance, both as predisposing elements, and above all, as triggering factors. Detailed models describing hydrological phenomena at hill-slope scale are complex and expensive. Alternatively, simpler conceptual or empirical models can be used. These models directly correlate rainfall and landslide occurrence and may give satisfactory results both in hazard analysis and real-time forecast. Empirical thresholds are defined collecting rainfall data for landslide meteoric events and for events without landslides. In this paper, the results of a hydrological model correlating the rainfall amount and the landslide occurrences in the Enna area (South Italy) are reported and discussed.

Recent developments for the seismic risk assessment

Thematic maps, such as seismic risk maps, are a useful tool that researchers use for representing the adverse outcomes that a natural catastrophic event can have over the territory. Generally, in those studies, major attention is focused in urban areas, where the human activities are concentrated. Main concerns are about the existing building stock, mostly composed by structures not compliant with modern seismic design criteria. The realization of a risk map is a complex task that involves the combination of data coming from different field of expertise, such as geology, geotechnical and structural engineering. The paper describes how the application of prospecting and surveying techniques (geological surveys, drilling, down-hole, MASW) allowed a decisive improvement in the geological knowledge of the area, contributing to define the subsoil model for the purposes of seismic microzonation. The interpretation of geophysical and geotechnical data and their correlation with geological units are explained and finally the microzonatic map is presented. The paper also reports the seismic geotechnical characterization executed with laboratory tests including the resonant column and cyclic torsional shear test on undisturbed samples. The results are summarized in terms of variation of stiffness and damping with shear strain. Finally, the use of wireless sensor technology for structural monitoring has significant benefits when the time available for access is often severely limited, by representing an effective way of managing risks once that an area of concern has been identified. The aim of the study is the acquisition of a local knowledge on issues related to seismic risk that may affect urban areas, through the acquisition, management and sharing of complex information. The available information, collected by sensor network, have been combined together in a Geographical Information System tool. The results provide a reliable representation of the seismic risk at urban scale to be used when planning the mitigation measures to be undertaken in order to improve the prevention and reduction of the disastrous effects of the earthquakes.

S tability Analysis of Landfills in Seismic Area

T he design of landfills includes stability analyses based on appropriate mechanical characterization of soil and Municipal Solid Waste (MSW). Particular attention must be devoted to MSW landfills in seismic areas, where the waste fill and liners can be damaged by the seismic loading, as documented by recent earthquakes. Then, to analyze the seismic stability of landfills, in addition to the dynamic characterization of soil, the dynamic properties of MSW are also required. With this aim, in situ and laboratory tests can be performed and static and dynamic properties can be evaluated. In this paper the results of a geotechnical investigation carried on the Cozzo Vuturo landfill in the Enna area (Sicily, Italy) are reported and analyzed. In particular, Seismic Marchetti Dilatomer Tests (SMDT) have been carried out for the seismic characterization of waste and the test results are used to derive shear wave velocity profiles and dynamic properties of the deposited waste materials. The behavior of the MSW landfill subjected to earthquake loading is modeled in terms of displacement

Liquefaction Resistance of Sandy Soils from Undrained Cyclic Triaxial Tests

Recent earthquakes frequently showed liquefaction of sandy soils. In these case one of the major challenges is the assessment of the residual strength of liquefied soil. Laboratory researches have clearly indicated that liquefaction susceptibility depend on many factors including soil grain size distribution, effective confining stresses and applied stress path in terms of cyclic shear stress amplitude. The complex cyclic shear stress path experienced by the soil during an earthquake can be reproduced in laboratory only by using sophisticated testing apparatuses. Cyclic triaxial tests have been widely used to asses soil liquefaction potential especially for coarse-grained soils, as in this study. In the framework of the design for the seismic retrofitting of the “Viadotto Ritiro” foundations along the A20 motorway connecting Messina with Palermo, a soil liquefaction study has been carried out. With this aim, a detailed geological and geotechnical characterization of the area has been performed by in situ and laboratory tests including the combined resonant column and torsional shear test and undrained cyclic triaxial tests (CTX). In particular, the paper presents the results of CTX, carried out on isotropically consolidated specimens carried out on specimens of a sandy soil to asses liquefaction strength. The results are plotted in terms of deviator stress q versus axial strain εa, cyclic stress ratio CSR and axial strain εa versus number of cycles Ncyc, effective mean stress p′ versus deviator stress q, cyclic stress ratio CSR and pore pressure ratio Ru versus number of cycles Ncyc. The results show that the cyclic resistance increases with the decrease in the initial confining stress and decreases as the silt content increases and confirme that the coarsest material has a lower tendency to liquefy.

Consequence analyses induced by landslides along transport infrastructures in the Enna area (South Italy)

In recent years, several landslides have had a strong impact on the road network, creating the need to define criteria for management and mitigation of hydrogeological risk through landslide zoning correlated with transport infrastructure systems. The reliability of transport infrastructures plays a key role since, in many cases, their inefficiency has caused serious damage to the anthropic system. Recently, advances in cloud computing have opened new opportunities in early warning and emergency management issues. The scientific community has recognized the added value of a geo-analytic approach in complex decision-making processes for critical situations due to natural events such as landslides. In this context, the research project CLARA [CLoud plAtform and smart underground imaging for natural Risk Assessment] has been developed. The main objective of the project is the acquisition of local knowledge on issues related to landslide risk that may affect urban areas, through the development of smart technologies that allow acquisition, management and sharing of complex information. The results provide a representation of the consequence analyses induced by landslides with reference to the Sicilian road network in the Enna area (southern Italy) to be used when planning the mitigation measures to be undertaken in order to improve the prevention and reduction of the disastrous effects of landslides.

Seismic risk: recent developments for the emergency management

he recent advances in cloud computing have opened new opportunities in emergency management issues due to earthquakes. In this context, Geographic Information System (GIS) based solutions have been recently investigated, with the aim of the prevention and the reduction of seismic risk. The paper focuses on the results of the research project PRISMA - cloud PlatfoRms for Interoperable SMArt Government in which an innovative open source GIS system, based on the knowledge in the field of dynamic characterization of soil has been developed in order to assess the local seismic hazard and the seismic zonation of the Enna area in the south of Italy. The paper describes how the application of prospecting and surveying techniques allowed a decisive improvement in the geological knowledge of the area, contributing to define the subsoil model for the purposes of seismic microzonation. The seismic geotechnical characterization has been performed with laboratory tests including the resonant column and cyclic torsional shear test on undisturbed samples. The interpretation of geophysical and geotechnical data and their correlation with geological units are presented as microzonatic map. Finally, a wireless sensor network has been used for structural monitoring at the aim to highlight the significant benefits when the time available for access is limited, by representing an effective way of managing risks. All the data relating to the monitoring of the buildings and to the geological and geotechnical characterization are available on the web GIS platform, representing an important tool for the prevention and reduction of the seismic risk.

Resonant column and torsional shear tests for the evaluation of the shear modulus and damping ratio of soil

The paper reports the results of the dynamic characterization of an industrial area of the municipality of Enna, where the Laboratory of Earthquake Engineering and Dynamic Analysis has been realized. A Resonant Column/Torsional Cyclic Shear apparatus to perform laboratory tests on soil samples retrieved from the site, has allowed to obtain the values of shear modulus G and damping ratio D as a function of the shear strain level γ. The experimental results are in good agreement with the well-known curves relating to soil with similar characteristics.