Alert threshold assessment based on equivalent displacements for the identification of potentially critical landslide events

Over the past years, the growing number of natural hazards all over the world has led to an increasing focus on activities aimed at studying and controlling the occurrence of these phenomena. In this context, monitoring systems have become a fundamental component for Landslide Early Warning Systems, allowing to understand the evolution of these processes and assess the need for dedicated mitigation measures. This result is achieved thanks to several technological advancements that led to the introduction of more accurate and reliable sensors, as well as automatic procedures for data acquisition and elaboration. However, despite these improvements, the data interpretation process is still a challenging task, in particular when it comes to the identification of critical events and failure forecasting operations. This paper presents a methodology developed to assess if a potentially critical event is displaying a significant deviation from previously sampled data, or if it could be classified as a false alarm. The process relies on the definition of a threshold value based on the landslide behavior preceding the event of interest. In particular, the reference value derives from the evaluation of equivalent displacements, defined as the displacements previously observed in a time interval equal to the one showed by the potentially critical event. This paper reports a series of examples referring to different case studies, involving both false alarms and real collapses, underlining the effectiveness of the proposed model as a useful tool to evaluate the landslide behavior with a near-real-time approach

A Factor Strength Approach for the Design of Rock Fall and Debris Flow Barriers

This paper discusses the applicability and the limitations of an approach to the limit states design of flexible barrier in which the soil/rock strength are factored as required in the European construction code. It shows as this approach has different implications if it is applied to the same kind of structure when loaded by different phenomena rockfall and debris flow in particular). Flexible barriers are common countermeasures to protect from rockfall hazard and to restrain debris flow events. Even if an intense scientific production has demonstrated the difference between the two phenomena, the protection systems are still often designed in the same way. Additionally, the Eurocode 7 (EC7), which is the European Standard concerning geotechnical design, has not been conformed to these kinds of structures and consequently a relationship between the reliability of the system and the partial factors does not exist. Since most of the parameters that rule these systems are not even considered in the code, the Authors propose the study of two cases, in which rockfall and debris flow occur, respectively, to analyse the applicability and the limitations of EC7 principles to design the suitable kind of structure

Monitoraggio delle temperature di scambiatori di calore coassiali in un sistema geotermico sperimentale

Nella progettazione di un sistema di estrazione di energia geotermica, il monitoraggio delle tem perature del sottosuolo riveste un ruolo di primaria importanza, in particolare per quanto riguarda i sistemi di superficie a bassa entalpia. Infatti, negli strati più superficiali del terreno, l’andamento della temperatura risulta variabile sia spazialmente che temporalmente a causa della sovrapposizione degli effetti di origine naturale (geotermica, solare) e antropica. Il sistema di monitoraggio che verrà presentato di seguito è stato installato con l’obiettivo di ottenere misure di temperatura in un impianto prototipale di questa tipologia, sviluppato mediante il Progetto Europeo GEOTeCH – Geothermal Technology for economic Cooling and Heating. Il sistema è costituito da uno strumento innovativo chiamato Therm Array, basato sulla tecnologia MUMS (Modular Un derground Monitoring System). Questo approccio consiste in una combinazione di sensori posizionati all’in terno di nodi (definiti Links), connessi mediante un cavo in fibra aramidica insieme ad un cavo elettrico, for mando una catena della lunghezza desiderata. Therm Array è stato sviluppato per il monitoraggio della temperatura del sottosuolo con sensori termometrici ad alta risoluzione, integrando procedure automatiche di acquisizione ed elaborazione dati. Il sito è strumentato con un totale di 3 Therm Array della lunghezza di 15 metri ciascuno, con spaziatura variabile tra i singoli sensori. Inoltre, sono state impiegate 4 sonde PT100 per il monitoraggio della temperatura all’interno delle condotte idriche. Le misure raccolte dal sistema di monitorag gio, installato a fine 2017 e tuttora attivo, sono di prezioso aiuto per la valutazione del potenziale di trasferi mento di calore delle sonde geotermiche verticali coassiali nel tempo e a varie profondità e degli impatti a medio lungo termine sul terreno di una pompa di calore sperimentale di tipo “dual source heat pump”, in grado cioè di decidere a quale fonte naturale attingere (aria, sottosuolo) a seconda delle necessità climatiche nei diversi periodi dell’anno

Anomaly pre-localization in distribution–transmission mains by pump trip: preliminary field tests in the Milan pipe system

In this paper, the reliability of transients due to pump trip as a powerful tool for the pre-localization of anomalies in real pipe systems is tested. The examined pipe system is part of the one supplying the city of Milan, Italy and is managed by Metropolitana Milanese SpA (MM). The characteristics of such a system can be considered as intermediate between those of classical transmission mains and distribution systems because of its several branches. A Lagrangian model simulating pressure wave propagation is used to evaluate the pipe pressure wave speed – associated with a genetic algorithm – and to locate possible anomalies – associated with wavelet analysis. The results of the diagnosis of the pipe system are corroborated by repairs executed by MM in the area where possible anomalies have been pre-localized

A multi-parameter field monitoring system to investigate the dynamics of large earth slides–earth flows in the Northern Apennines, Italy

Large earth slides and rocks lides evolving into earth flows are quite widespread in the Northern Italian Apennines. Despite being simply referred to as landslides, many of them are, in fact, large complexes of landslides. They evolved through multiple and/or successive movements, undergoing partial and/or total reactivations. The reactivation of pre-existing landslide bodies is the prevalent mechanism for the known landslide events, as the historical records and the technical reports indicate. Landslide reactivation is, indeed, a relevant topic from the perspective of risk assessment and mitigation. A multi-parameter monitoring system was installed on a large complex of landslides that underwent partial or total reactivations after heavy rainfall events, causing damages to buildings and infrastructures. Two clusters of automatic piezometers—each coupled with an inclinometer—and a time-lapse resistivity deployment were the core of the monitoring system. A weather station, collecting data from subsurface thermometers, and a water content probe completed the system. After the construction of a new geological model of the slope, this study aimed at understanding the possible mechanisms leading to the reactivation of the landslide. This goal was achieved by gaining insights into the process of rainfall infiltration into the landslide deposits, by determining the groundwater flow and evaluating the landslide displacements. The monitoring system captured the processes that took place in the landslide bodies and the bedrock in response to a rainfall event in early February 2017, which followed a dry period of eight months. The recorded data provided indications on the variation of the hydraulic head in the groundwater within the landslide and the bedrock, particularly at the sliding surfaces. The electrical conductivity of the groundwater and the resistivity of the terrain varied across the failure surfaces. In particular, a sudden increase in the electrical conductivity was related to the locations of the main sliding surfaces. The joint analysis of time-lapse resistivity, hydraulic heads, and groundwater electrical conductivity helped identify the locations of weaker levels within the landslide masses, which were confirmed by data from inclinometers. This study improved the knowledge of the hydrogeological behaviour of a complex of landslides in heterogeneous low-permeability media. Moreover, the obtained results contributed to the understanding of the role played by different portions of the landslide complex in the evolution of the movement

Laparoscopic splenectomy as a definitive management option for high-grade traumatic splenic injury when non operative management is not feasible or failed: a 5-year experience from a level one trauma center with minimally invasive surgery expertise

Technique, indications and outcomes of laparoscopic splenectomy in stable trauma patients have not been well described yet. All hemodynamically non-compromised abdominal trauma patients who underwent splenectomy from 1/2013 to 12/2017 at our Level 1 trauma center were included. Demographic and clinical data were collected and analysed with per-protocol and an intention-to-treat comparison between open vs laparoscopic groups. 49 splenectomies were performed (16 laparoscopic, 33 open). Among the laparoscopic group, 81% were successfully completed laparoscopically. Laparoscopy was associated with a higher incidence of concomitant surgical procedures (p 0.016), longer operative times, but a significantly faster return of bowel function and oral diet without reoperations. No significant differences were demonstrated in morbidity, mortality, length of stay, or long-term complications, although laparoscopic had lower surgical site infection (0 vs 21%).The isolated splenic injury sub-analysis included 25 splenectomies,76% (19) open and 24% (6) laparoscopic and confirmed reduction in post-operative morbidity (40 vs 57%), blood transfusion (0 vs 48%), ICU admission (20 vs 57%) and overall LOS (7 vs 9 days) in the laparoscopic group. Laparoscopic splenectomy is a safe and effective technique for hemodynamically stable patients with splenic trauma and may represent an advantageous alternative to open splenectomy in terms of post-operative recovery and morbidit