Davide Brambilla

Surface and subsurface non-invasive investigations to improve the characterization of a fractured rock mass

Three-dimensional assessment and modelling of fractured rock slopes is a challenging task. The reliability of the fracture network definition is of paramount importance for several engineering and geotechnical applications, and so far, different approaches have been proposed to improve the assessment procedure. A thorough knowledge of the actual fracture system is necessary to construct an accurate geometrical model of the rock mass and to determine block size distribution within the rock body. This paper describes the integration of diverse techniques used to define the rock mass fracture pattern, focusing on the most important fracture features, which are joint orientation, spacing, and persistence. A case study in the north of Italy was selected in order to show the potential of an integrated approach where surface and subsurface investigations are coupled. The rock surface was analysed by means of both standard geological mapping and terrestrial laser scanning. Ground penetrating radar surveys were conducted to image and map the discontinuity planes inside the rock mass and to estimate fracture persistence. The results obtained from the various investigation methodologies were employed to construct a model of the rock mass. This approach may lead to a better understanding of fracture network features, usually observed only on the rock surface. A careful analysis of block size distribution in a rock body can be of valuable help in several engineering and risk mitigation applications.

Monitoring Riverbank Erosion in Mountain Catchments Using Terrestrial Laser Scanning

Sediment yield is a key factor in river basins management due to the various and adverse consequences that erosion and sediment transport in rivers may have on the environment. Although various contributions can be found in the literature about sediment yield modeling and bank erosion monitoring, the link between weather conditions, river flow rate and bank erosion remains scarcely known. Thus, a basin scale assessment of sediment yield due to riverbank erosion is an objective hard to be reached. In order to enhance the current knowledge in this field, a monitoring method based on high resolution 3D model reconstruction of riverbanks, surveyed by multi-temporal terrestrial laser scanning, was applied to four banks in Val Tartano, Northern Italy. Six data acquisitions over one year were taken, with the aim to better understand the erosion processes and their triggering factors by means of more frequent observations compared to usual annual campaigns. The objective of the research is to address three key questions concerning bank erosion: “how” erosion happens, “when” during the year and “how much” sediment is eroded. The method proved to be effective and able to measure both eroded and deposited volume in the surveyed area. Finally an attempt to extrapolate basin scale volume for bank erosion is presented.

A new geological model for Spriana landslide

Complex large landslides are characterized by different kinematic behaviors and involve diverse materials. Both elements make it difficult to study the instability of these huge mass movements, which may cause massive damage and affect extended areas. This paper is focused on the study of Spriana landslide, an important rockslide located in the North of Italy. Starting from the geological interpretation provided by Belloni and Gandolfo (Geologia tecnica ed ambientale 3:7–36, 1997), the authors gather all available data sets and perform a novel analysis aimed to better describe the unstable body. The key point of this case study regards the characterization of the deeper surface of failure. The location as well as the continuity of this surface is a crucial unsolved question, and in this paper we try to provide a reasonable answer. We propose a new hypothesis based on a structurally controlled, wedge-like rockslide involving the presence of a composed deeper surface of failure constrained by the intersection of two different weak zones. Although this work mainly addresses the development of a new geological model, numerical simulations were also performed. Both continuous and discontinuous models were tested, and then a comparison of the outcomes of the numerical simulations was performed to define the best fit to the observed landslide behavior.

On integrated sediment transport modelling for flash events in mountain environments

Sediment production and transport in mountain basins during short-term, intense events depend on a variety of processes. Available models typically consider a limited portion of the phenomenological chain, frequently either sediment supply or solid transport along the waterways. On the other hand, proper depiction of on-site processes requires ability to model all the process stages and suitable integration between different models. In this manuscript, an integrated modelling is attempted for small catchments in Italian Alpine foothills. The integrated approach has involved: (i) hydrologic estimation of peak discharge, (ii) evaluation of the volumetric sediment supply into the stream, and (iii) computation of the morphologic evolution of the river bed. The results are discussed focussing on: (i) the feasibility of a joint modelling like the one presented, in the light of all the limitations imposed by the different nature of hillslope-devoted and river-devoted models; and (ii) the sensitivity of the obtained results to some parameters, for an assessment of result reliability.

Collective Perception of Environmental Features in a Robot Swarm

In order to be effective, collective decision-making strategies need to be not only fast and accurate, but sufficiently general to be ported and reused across different problem domains. In this paper, we propose a novel problem scenario, collective perception, and use it to compare three different strategies: the DMMD, DMVD, and DC strategies. The robots are required to explore their environment, estimate the frequency of certain features, and collectively perceive which feature is the most frequent. We implemented the collective perception scenario in a swarm robotics system composed of 20 e-pucks and performed robot experiments with all considered strategies. Additionally, we also deepened our study by means of physics-based simulations. The results of our performance comparison in the collective perception scenario are in agreement with previous results for a different problem domain and support the generality of the considered strategies.

A simplified early-warning system for imminent landslide prediction based on failure index fragility curves developed through numerical analysis

Early-warning systems (EWSs) are crucial to reduce the risk of landslide, especially where the structural measures are not fully capable of preventing the devastating impact of such an event. Furthermore, designing and successfully implementing a complete landslide EWS is a highly complex task. The main technical challenges are linked to the definition of heterogeneous material properties (geotechnical and geomechanical parameters) as well as a variety of the triggering factors. In addition, real-time data processing creates a significant complexity, since data collection and numerical models for risk assessment are time consuming tasks. Therefore, uncertainties in the physical properties of a landslide together with the data management represent the two crucial deficiencies in an efficient landslide EWS. Within this study the application is explored of the concept of fragility curves to landslides; fragility curves are widely used to simulate systems response to natural hazards, i.e. floods or earthquakes. The application of fragility curves to landslide risk assessment is believed to simplify emergency risk assessment; even though it cannot substitute detailed analysis during peace-time. A simplified risk assessment technique can remove some of the unclear features and decrease data processing time. The method is based on synthetic samples which are used to define the approximate failure thresholds for landslides, taking into account the materials and the piezometric levels. The results are presented in charts. The method presented in this paper, which is called failure index fragility curve (FIFC), allows assessment of the actual real-time risk in a case study that is based on the most appropriate FIFC. The application of an FIFC to a real case is presented as an example. This method to assess the landslide risk is another step towards a more integrated dynamic approach to a potential landslide prevention system. Even if it does not define absolute thresholds, the accuracy is satisfactory for a preliminary risk assessment, and it can provide more lead-time to understand the hazard level in order to make decisions as compared with a more sophisticated numerical approach. Hence, the method is promising to become an effective tool during landslide emergency.

Evaluation of sediment yield from valley slopes: a case study

Hydro-geological hazards in alpine areas is a really common problem. Many calamitous phenomena (such as debris flows, landslides, and others) are related to the sediment yield from the slopes of the valleys. Sediment yields are far from being fully understood and predictable, due to a lack of knowledge of the physical mechanisms underlying these processes and to the variability of the peculiar geomorphologic characteristics of river basins. Key unknowns are the medium- and long-term average sediment production, the recharge time of the sediment sources (and consequently the frequency of the yields), the triggering factors and the thresholds for activation. The manuscript documents the results of the estimation of sediment production for the basin of the Tartano valley in northern Italy. The basin is characterized by a significant presence of weak rocks (cataclastic, mylonitic), that makes considerable amounts of loose sediments available. In this work, semi-quantitative models were applied to evaluate the basin-scale, yearly sediment yield. Estimates sediment volumes were compared to records of sediment volumes extracted from an artificial reservoir located at the downstream section of the catchments. In addition, the spatial distribution of the sediment instability level was obtained, highlighting a significant heterogeneity of the river basin. Therefore, the relevance of the basin-scale modelling of sediment yields for off-site and on-site processes was discussed. The dependency of the sediment yield regime on the spatial and temporal scale supporting the evaluations was analyzed and discussed.

The risk of collapse in abandoned mine sites: the issue of data uncertainty

Abstract Ground collapses over abandoned underground mines constitute a new environmental risk in the world. The high risk associated with subsurface voids, together with lack of knowledge of the geometric and geomechanical features of mining areas, makes abandoned underground mines one of the current challenges for countries with a long mining history. In this study, a stability analysis of Montevecchia marl mine is performed in order to validate a general approach that takes into account the poor local information and the variability of the input data. The collapse risk was evaluated through a numerical approach that, starting with some simplifying assumptions, is able to provide an overview of the collapse probability. The final results is an easy-accessible-transparent summary graph that shows the collapse probability. This approach may be useful for public administrators called upon to manage this environmental risk. The approach tries to simplify this complex problem in order to achieve a roughly risk assessment, but, since it relies on just a small amount of information, any final user should be aware that a comprehensive and detailed risk scenario can be generated only through more exhaustive investigations.

On Analysis Of Sediment Sources Toward Proper Characterization Of Hydro-geological Hazard For Mountain Environments

Event-induced sediment yield from mountain valley slopes to rivers may represent a problem for landscape safety if the total sediment volume supplied is larger than the transport capacity of the water courses, leading to riverbed aggradation and increased water levels. Multiple sediment sources are normally present in mountain basins; the former are characterized by different spatial and temporal scales, which makes a global analysis hardly possible. On the other hand, modeling of sediment yield furnishes the necessary boundary condition for that of sediment transport in rivers. In this study, several types of sediment sources were separately analyzed with reference to the Tartano basin, located in Northern Italy. A detailed analysis of the sediment volume from soil erosion and some preliminary analyses of a faulted valley were performed. The transport capacity of the major water courses was computed around the confluence among them, for comparison with the estimated yields. The analysis showed that not all the sediment sources contribute significantly to the solid volumes that must then be transported by the rivers. This enables simplified models to be used considering only the yields that are expected to represent a major load. It is hypothesized that such fi nding be valid for other basins, of course considering the specific features of each. Keywords hydro-geological risk, mountain basin, sediment transport, sediment yield Language: en

New Investigations to Update the Model of the Premana (LC) Landslide

Deep seated landslides have historically caused extensive damage to land and structures. These large failures are usually controlled by several triggering factors, and one of the most important is deemed to be the change in pore-water pressure inside the slope.