Papers by Andrea Segalini
A variational approach is used to study the stability of a soap film spanning a flexible loop. Th... more A variational approach is used to study the stability of a soap film spanning a flexible loop. The film is modeled as a fluid surface endowed with constant tension and the loop is modeled as an inextensible and unshearable elastic rod that resists not only bending but also twisting about the tangent to its centerline. The first and second variations of the underlying energy functional are derived, leading to governing equilibrium equations and energetically based stability conditions. The latter conditions are applied to explore the effect of subjecting flat circular configurations to planar and transverse perturbations. Both the areal stretching and the lineal twisting prove to compete against the lineal bending to destabilize such a configuration. Experiments are performed to study post-buckled configurations and to assess the validity of the theoretical predictions.
Numerical modeling of time dependant – slow moving – landslides in colluvium
Studies aimed to the consolidation of the cliff where the middleage Corniglio town in built
Application of a New Generalized Method to Assess Alert Thresholds for Landslides
Springer eBooks, 2022
Civil and Environmental Engineering
At the beginning of the 16th century, the original inhabitants of Čachtice built a large complex ... more At the beginning of the 16th century, the original inhabitants of Čachtice built a large complex of tunnels and cellars under the village, today called the Čachtice underground. The underground protected people from war conflicts, most recently during World War II, as anti-aircraft shelters. Over time, the underground lost its significance. The corridors were walled up, covered with rubble, and collapsed due to construction work. Later, a part of the underground was repaired, and historical events occurred in such a preserved part. Due to a lawsuit, the Čachtice underground was eventually closed to the public, and it was necessary to test the stability of the walls of the Čachtice underground. A 3D model of the underground was created, and three areas were identified in which numerical calculations were performed in Plaxis 2D software. The whole underground is located in loess soil. The Čachtice underground is stable if the conditions do not change diametrically. The calculated fact...
Experimental study for the design of flexible barriers under debris flow impact
CRC Press eBooks, Apr 17, 2018
Debris flows are wide spread phenomena in mountain areas and due to their high velocity and kinet... more Debris flows are wide spread phenomena in mountain areas and due to their high velocity and kinetic energy, are very destructive processes in terms of human life and structures.Several studies have been dedicated to both triggering and propagation phases of a mass movement but there is still a lack of knowledge about the behavior of the flow during its impact against an obstacle.In particular, the crucial point is the definition of the impact action, fundamental to design protection barriers, that depends on the flow nature and propagation characteristics (velocity and thickness). These entities are difficult to be determined by means of experimental measurement and consequently several empirical and theoretical relations were proposed in literature. Laboratory tests on scaled channel are also available but they are often affected by the limitation of the scale effects. The aim of this paper is to analyze in detail the impact of a debris flow against an obstacle and present a new method to design these protection structures: this method combines the numerical method DAN and the Brighenti's method in order to evaluate the flow characteristics and quantify the action applied to the barrier. Laboratory tests have allowed for model calibration and for the validation of the hypothesis about the nature of the impact
Application of Modular Underground Monitoring System (MUMS) to Landslides Monitoring: Evaluation and New Insights
Springer eBooks, 2015
The paper describes the application of the Modular Underground Monitoring System (further referre... more The paper describes the application of the Modular Underground Monitoring System (further referred as MUMS) (Segalini et al. 2013) in two active landslides located in the Northern Italian Apennines. In particular, the aim of the paper is to demonstrate the efficiency and accuracy of the system and to examine the advantages of an automated semi-continuous monitoring for the comprehension of the mechanical behavior of landslides, the definition of their triggering factors and the correct evaluation of their short term velocity. The mechanical behavior of slow moving landslides is generally evaluated on the basis of traditional surveys which are carried out at long time interval and therefore are lacking of detailed information about the links between triggering causes and mechanical effects. The main advantage of an automated monitoring system resides in the observation frequency and in the simultaneous recording of several physical entities such as deformation, precipitation, pore pressure and so on. This large amount of data can be used for the numerical evaluation of the landslide behavior and for the definition of the most significant triggering cause(s). The obtained knowledge is of fundamental importance when there is a need of establishing an hazard threshold for the particular landslide and, when this assumption is made, the automated monitoring system can immediately become a real time control and alarm triggering device. For this purpose, it is important that the lifespan of the instrumentation is as long as possible, in relation with the expected displacements, in order to maintain the real time monitoring effective and economical as well as to build a reliable database for statistical analysis.
13th ISRM International Congress of Rock Mechanics, 2015
The topic of this study is the design of flexible fences to mitigate the risk due to debris flow ... more The topic of this study is the design of flexible fences to mitigate the risk due to debris flow phenomena by means of theoretical and experimental studies analysed in framework of the Rock Engineering System (RES). The study of the interaction between debris flows and flexible barriers is a major challenge since many different aspects concerning both the slope characteristics and the structure features are involved. Debris flows are often triggered by the mobilization of debris deposits that are generated by rock fall of adjacent rock walls. The rock debris deposits are difficult to be characterized by the physical and mechanical point of view due to their large variability in volume distribution and, moreover, when dealing with high mountains environment, they are also strongly affected by the presence of water at different phases (solid or liquid) depending on the temperature. The debris deposit turns unstable in relation with the geotechnical and environmental features of the areas and the instability evolution in high mountain steep valley is often a debris flow. Debris flow destructive potential is very high and protections are often needed to reduce the debris flow risk. This complexity determines the needs of comprehensive study able to include the global basin dynamic and the environmental conditions. An a-priori analysis of the influence of the different aspects can be useful to focus on the real driving aspects of the problem. Due to the complexity of the system the application of the RES methodology is recommended in order to clearly define the different assumptions needed, their influence on the simulations and a comparison among them. RES allows investigating triggering criteria, flow and depositional processes and interaction of flows with protection fences in a rational way. For this purpose, an interaction matrix is created: it summarizes the key geotechnical parameters that influence debris flows, their interactions and debris/engineering protection opera behaviour. The goal is to quantify the diagonal-off terms to assess the residual risk after barrier construction, using back analysis from real debris flow event and data collection from literature. This methodology is applied to analyze a debris flow event in the Italian Western Alps where numerical analyses are carried on to assess flow characteristics to be used for fence design through the application of an analytical and numerical model developed by the authors (Brighenti et al, 2013). In particular, the velocity and deposition heights have been estimated using the numerical code RASH3D (Pirulli, 2010), which is a single-phase model based on depth-averaged Saint Venant equations. Pathways of different lengths are studied to assess the input data necessary to design the protection barrier and to determine the associated risk. Simulation of the barrier at different places along the valley will also allow to determine optimal barrier location in terms of minimum residual risks by comparing the velocity, the volume and the energy of the debris after the barrier impact. The work will produce a possible design scheme to be adopted in this environment.
Natural Hazards and Earth System Sciences, Jul 22, 2016
The aim of this paper is to analyse debris flow impact against rigid and undrained barrier in ord... more The aim of this paper is to analyse debris flow impact against rigid and undrained barrier in order to propose a new formulation for the estimation of acting force after the flow impact to safe design protection structures. For this reason, this work concentrates on the flow impact, by performing a series of small scale tests in a specifically created flume. Flow characteristics (flow height and velocity) and applied loads (dynamic and static) on barrier were measured using four ultrasonic devices, four load cells and a contact surface pressure gauge. The results obtained were compared with main existing models and a new equation is proposed. Furthermore, a brief review of the small scale theory was provided to analyse the scale effects that can affect the results.
Impact identification on flexible rockfall barriers: on site test of a wireless monitoring system
IOP conference series, 2023
Flexible rockfall barriers represent an effective measure to mitigate hazard related to falling b... more Flexible rockfall barriers represent an effective measure to mitigate hazard related to falling boulders. The monitoring activity of these protection structures is essential to guarantee their functionality, and usually aims to verify the barrier conditions and to identify any impact on the net. The system here presented, called D-Fence, was specifically developed for the realtime monitoring of flexible rockfall barriers. It consists of a series of separate battery-powered devices installed on the uprights of the monitored structure and transmit data to the elaboration center through a wireless local network. Each module includes a 3D tilt sensor, allowing the near real-time monitoring of the rotation of the uprights, while the integration of a shock sensor makes it possible to measure in real-time the accelerations experienced by the barrier. The onsite test of the D-Fence system involved the installation of four modules on a prototype barrier located in a pilot site in Northern Italy. Each device was placed on a different upright and was connected to a local Wi-Fi network. In this configuration, two different concrete boulders were dropped on the barrier in order to test the D-Fence ability to measure the tilt variation of the uprights and identify the overcoming of a predefined acceleration threshold.
Integrated analysis of data collected by an innovative monitoring system and results of a 3D numerical model in Boschetto landslide
Numerical and experimental analysis of debris flow protection fence efficiency
Landslides, Feb 13, 2019
Understanding the mechanism of a landslide and its evolution is of fundamental importance in the ... more Understanding the mechanism of a landslide and its evolution is of fundamental importance in the risk management process. This work introduces an articulated approach to the problem, applying it to a specific case in the south of Italy where a gravitational movement insists on a section of an important highway. In recent years, the site has been investigated from a geomorphological and a lithological point of view, and a comprehensive geomechanical characterization has been carried out by means of on-site and laboratory tests. The area has been instrumented with a monitoring system composed of automatic inclinometers, piezometers, a rainfall station, and time domain reflectometry (TDR) cables. These sensors have monitored the deformation processes and their correlation with groundwater fluctuation. A 2D finite differences model (FDM) of the slope has been created, calibrated, and validated through back analysis, carried out using the monitoring data available. A secondary creep phenomenon, barely influenced by the water level rise due to occasional rainfall, has been identified and modeled using the Burgers viscoelastic constitutive model. Variations in the piezometric level were introduced and their effect accounted for the numerical model refinement. Once the improvements had been completed together with the reproduction of past events, a predictive analysis was carried out in order to forecast the most probable slope behavior relative to the incoming year. At the end of this phase, the infrastructure supervisor should have information about possible deformations to be compared with the near realtime monitoring outcomes and design assumptions. This procedure allows real-time monitoring of the compatibility of slope deformations with highway safety.
Natural Hazards, Sep 15, 2022
Over the past years, the growing number of natural hazards all over the world has led to an incre... more 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.
Algorithms for the Near-Real Time Identification and Classification of Landslide Events Detected by Automatic Monitoring Tools
Lecture notes in civil engineering, 2023
Revision of the Eurocodes – Aspects of Geotechnical and Rock Engineering Design
ISRM International Symposium - EUROCK 2020, Jun 14, 2020
Communications - Scientific letters of the University of Zilina, 2014
The paper illustrates the theoretical basis of a new device called MUMS-Modular Underground Monit... more The paper illustrates the theoretical basis of a new device called MUMS-Modular Underground Monitoring System-and one of its applications. MUMS has been designed for monitoring of underground displacements through a continuous and automated data acquisition system. MUMS instrumentation can be used to monitor the deformation of natural and artificial slopes as well as geotechnical structures. The device consists of a series of nodes located at known distances along a connecting rope and is installed within a vertical borehole. Each node measures its local rotation relative to the vertical axis by means of a 3D micro electro-mechanical acceleration sensor (MEMS). The direction cosines of each node are calculated in order to determine the 3D shape and deformation of the entire borehole. The paper illustrates an interesting application of MUMS in natural slopes and points out the benefits of the system.
Monitoring of preconvergence deformations in a road tunnel: data analysis and validation
IOP Conference Series: Earth and Environmental Science, 2021
Tunnels are complex constructions, generally built in difficult geological contexts. When dealing... more Tunnels are complex constructions, generally built in difficult geological contexts. When dealing with underground structures, the study of ground deformations is a key aspect to consider in order to guarantee safety during the tunnel excavation and construction quality. One of the main aspects to investigate is related to the development of preconvergence phenomena in the advance core, i.e. deformations involving the volume of rock mass ahead of the tunnel face. This paper presents the application of a new monitoring tool specifically developed to measure preconvergence effects during the excavation phases with a direct approach. The device, called PreConv Array, consists of a series of 3D MEMS (Micro Electro-Mechanical System) and temperature sensors. The system takes advantage of automated procedures for data acquisition, elaboration, and representation, thus achieving a near-real time monitoring of the ground differential vertical settlements ahead of the excavated face. Monitor...
Debris flow impact on a flexible barrier: laboratory flume experiments and force-based mechanical model validation
Natural Hazards, 2021
Nowadays, hydrogeological instability is a very critical issue because of its impact on populatio... more Nowadays, hydrogeological instability is a very critical issue because of its impact on population, infrastructures and economic and productive sectors. This makes essential to use advanced and reliable defense technologies, which are able to guarantee high performance and reliability. Flexible and permeable structures are ideal for stopping natural phenomena like debris flow, thanks to their high deformation capacity and their water permeability. This study presents some results obtained from laboratory tests related to the impact of a simulated debris flow against a scaled physical model of the barrier. A granular flow composed of aggregates of known size particle was released in a channel with variable inclination and known length and height. Using this experimental setup, several tests were carried out by varying the inclination of the channel and the geometry of the barrier. The results obtained were correlated with data deriving from a simplified analytical model; the comparison between the measured and calculated values made possible to assess the good prediction capability of the model, providing a simple and innovative tool to design and assess the safety of deformable protection barriers.
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Papers by Andrea Segalini