Backanalysis methodology based on multiple optimization techniques for geotechnical problems

Nowadays, thanks to the increase of computers capability to solve huge and complex problems, and also thanks to the endless effort of the geotechnical community to define better and more sophisticated constitutive models, the challenge to predict and simulate soil behavior has been eased. However, due to the increase in that sophistication, the number of parameters that define the problem has also increased. Moreover, frequently, some of those parameters do not have a real geotechnical meaning as they just come from mathematical expressions, which makes them difficult to identify. As a consequence, more effort has to be placed on parameters identification in order to fully define the problem. This thesis aims to provide a methodology to facilitate the identification of parameters of soil constitutive models by backanalysis. The best parameters are defines as those that minimize an objective function based on the differences between measurements and computed values. Different optimization techniques have been used in this study, from the most traditional ones, such as the gradient based methods, to the newest ones, such as adaptive genetic algorithms and hybrid methods. From this study, several recommendations have been put forward in order to take the most advantage of each type of optimization technique. Along with that, an extensive analysis has been carried out to determine the influence on soil parameters identification of what to measure, where to measure and when to measure in the context of tunneling. The Finite Element code Plaxis has been used as a tool for the direct analysis. A FORTRAN code has been developed to automate the entire backanalysis procedure. The Hardening Soil Model (HSM) has been adopted to simulate the soil behavior. Several soil parameters of the HSM implemented in Plaxis, such as E_50^ref, E_ur^ref, c and f, have been identified for different geotechnical scenarios. First, a synthetic tunnel case study has been used to analyze all the different approaches that have been proposed in this thesis. Then, two complex real cases of a tunnel construction (Barcelona Metro Line 9) and a large excavation (Girona High-Speed Railway Station) have been presented to illustrate the potential of the methodology. Special focus on the influence of construction procedures and instruments error structure has been placed for the tunnel backanalysis, whereas in the station backanalysis, more effort has been devoted to the potential of the concept of adaptive design by backanalysis. Moreover, another real case, involving a less conventional geotechnical problem, such as Mars surface exploratory rovers, has been also presented to test the backanalysis methodology and the reliability of the Wong & Reece wheel-terrain model; widely adopted by the terramechanics community, but nonetheless, still not fully accepted when analyzing lightweight rovers as the ones that have been used in recent Mars exploratory missions.Actualmente, gracias al aumento de la capacidad de los ordenadores para resolver problemas grandes y complejos, y gracias también al gran esfuerzo de la comunidad geotécnica de definir mejores y más sofisticados modelos constitutivos, se ha abordado el reto de predecir y simular el comportamiento del terreno. Sin embargo, debido al aumento de esa sofisticación, también ha aumentado el número de parámetros que definen el problema. Además, frecuentemente, muchos de esos parámetros no tienen un sentido geotécnico real dado que vienen directamente de expresiones puramente matemáticas, lo cual dificulta su identificación. Como consecuencia, es necesario un mayor esfuerzo en la identificación de los parámetros para poder definir apropiadamente el problema. Esta tesis pretende proporcionar una metodología que facilite la identificación mediante el análisis inverso de los parámetros de modelos constitutivos del terreno. Los mejores parámetros se definen como aquellos que minimizan una función objetivo basada en la diferencia entre medidas y valores calculados. Diferentes técnicas de optimización han sido utilizadas en este estudio, desde las más tradicionales, como los métodos basados en el gradiente, hasta las más modernas, como los algoritmos genéticos adaptativos y los métodos híbridos. De este estudio, se han extraído varias recomendaciones para sacar el mayor provecho de cada una de las técnicas de optimización. Además, se ha llevado a cabo un análisis extensivo para determinar la influencia sobre qué medir, dónde medir y cuándo medir en el contexto de la excavación de un túnel. El código de Elementos Finitos Plaxis ha sido utilizado como herramienta de cálculo del problema directo. El desarrollo de un código FORTRAN ha sido necesario para automatizar todo el procedimiento de Análisis Inverso. El modelo constitutivo de Hardening Soil ha sido adoptado para simular el comportamiento del terreno. Varios parámetros del modelo constitutivo de Hardening implementado en Plaxis, como E_50^ref, E_ur^ref, c y f, han sido identificados para diferentes escenarios geotécnicos. Primero, se ha utilizado un caso sintético de un túnel donde se han analizado todas las distintas técnicas que han sido propuestas en esta tesis. Después, dos casos reales complejos de una construcción de un túnel (Línea 9 del Metro de Barcelona) y una gran excavación (Estación de Girona del Tren de Alta Velocidad) se han presentado para ilustrar el potencial de la metodología. Un enfoque especial en la influencia del procedimiento constructivo y la estructura del error de las medidas se le ha dado al análisis inverso del túnel, mientras que en el análisis inverso de la estación el esfuerzo se ha centrado más en el concepto del diseño adaptativo mediante el análisis inverso. Además, otro caso real, algo menos convencional en términos geotécnicos, como es la exploración de la superficie de Marte mediante robots, ha sido presentado para examinar la metodología y la fiabilidad del modelo de interacción suelo-rueda de Wong y Reece; extensamente adoptado por la comunidad que trabajo en Terramecánica, pero aún no totalmente aceptada para robots ligeros como los que se han utilizado recientemente en las misiones de exploración de Marte

Beyond the deterministic approach - on the feasibility of data assimilation methods in geotechnics

The surge in economic and social development has resulted in significant challenges, especially for linear physical infrastructure. A substantial part of the ageing physical linear infrastructure has been built on problematic soils and often have poorly documented foundation solutions. A typical example is the case of embankments for infrastructure on soft ground conditions. Soft soils possess various important characteristics that contribute to their complex emerging soil response when subjected to hydro-mechanical loading. In recent times, numerous advanced constitutive models grounded in various theories and hypotheses have emerged to capture the behaviour of soft soils. These models differ from models commonly used in geotechnical engineering, as they encompass complex soft soil features, \eg anisotropy, rate-dependency and degradation of bonding that enable reasonably accurate predictions for test data obtained under controlled laboratory conditions. However, their applicability for making informed decisions on large-scale field projects may be limited, as deterministic calculations alone may not adequately consider the variability in the behaviour of geomaterials encountered in real-world scenarios. Furthermore, not all model parameters have direct geotechnical significance as they are derived solely from mathematical expressions, posing challenges in their identification. With the growing utilisation of advanced constitutive models in engineering analysis, the input parameters for these models take on crucial roles as design parameters. This thesis provides a probabilistic methodology that enables the identification of parameters of constitutive models for geotechnics, through inverse analysis using Data Assimilation (DA). The primary objective of this thesis is to evaluate the applicability of existing Data Assimilation concepts in the field of geotechnical engineering. To achieve this, a modular framework that allows the implementation and use of multiple DA methods in conjunction with geotechnical numerical codes is created. A comprehensive and systematic comparison of contemporary state-of-the-art DA schemes specific to geotechnical engineering is performed along with examining the factors influencing their performance. Additionally, hybridisation of meta-heuristic algorithms with classical Data Assimilation methods has also been proposed to improve some of the observed drawbacks. In this thesis, the limitations of the deterministic approach has been demonstrated and the need for a robust probabilistic tool is shown to be paramount. It has also shown that it is time to start embracing the value of monitoring data which can be put to efficient use when a robust probabilistic framework like Data Assimilation is considered

Application of new observational method on deep excavation retaining wall design in London Clay

Ground engineering in urban areas faces the great challenge of balancing the increasing demand for underground space against safety and asset protection while avoiding high construction costs. This study shows savings can be achieved on embedded retaining wall design for deep excavation in London Clay through the observational method, without compromising safety. Despite the inherent benefits of the method and its acceptance by design codes, the application of the observational method for excavation design has been slow and inconsistent due to the lack of guidance, in addition to other difficulties. This research aims to promote the application of the observational method in excavation design by proposing a new framework. The framework with four design approaches is established based on the review of historical excavation case histories and four Crossrail station excavations using the observational method. The term Ab initio is used for excavation design from the beginning of construction, covering Optimistic Approach A and Cautious Approach B. The term Ipso-tempore is introduced for excavation redesign after construction starts, comprising a newly defined Pro-active Approach C and the ‘best-way-out’ or Reactive Approach D. Back-analysis is critical in the observational method. The whole process of back analysis is examining monitoring systems (observations) and predictions by the numerical analysis with the adopted soil constitutive models. Three Crossrail excavation cases are back-analysed by the Mohr-Coulomb model using FEMs from Pseudo-FEM to 2D and 3D FEMs. The Crossrail Tottenham Court Road Station, Western Ticket Hall deep box excavation is also back-analysed by the BRICK model using the 3D FEM, representing the advanced soil model. The above back-analysis results are presented including the calibrated most probable soil model parameters. The different results indicate the back-analysis is subject to the type of numerical analysis, the adopted soil constitutive model, also it needs to be tailored to the monitoring data used for comparison. A reassessment of the TCR-WTH excavation design by Approach A is carried out using the semi-FEM with the Mohr-Coulomb model. The optimistic design with the calibrated most probable Mohr-Coulomb parameters shows over 30% saving in construction materials, which is supported by the contingency plan with the characteristic Mohr-Coulomb parameters if the excavation does not encounter the expected conditions. Improvements of specifications for the instruments and monitoring data are recommended to provide more reliable monitoring data.Ove Arup and Partner

Rad ne sadrži naslov na drugom jeziku.

Factors primary controlling rainfall-induced slope failures are both rainfall characteristics and soil properties. Rainfall causes a transient infiltration process through the unsaturated part of the slope which affects sloping material by increasing the moisture content and pore-water pressure, changing the effective stress and hydro-mechanical properties of the soil. To study the physical process of rainfall infiltration and how it affects the slope stability state, the dependency between water retention properties, hydraulic permeability, shear strength properties and the water content or negative pore-water pressures existing above the phreatic surface have to be known. Unlike for the shallow-type landslides, very few studies were performed for the case of deep-seated landslides built of material with relatively low hydraulic conductivity. This kind of studies were never performed for landslides occurring in flysch deposits. This study presents the results of different field investigations, laboratory tests, and numerical activities that were performed to build up a numerical model capable to determine the influence of rainfall infiltration process on slope stability state through time. Undisturbed samples of the residual soil from a flysch rock mass were used to perform different laboratory tests in saturated and unsaturated conditions, aimed to provide an advanced hydro-mechanical characterization of the soil behavior under negative pore-water pressure. For the first time, the water retention curves, hydraulic conductivity functions, and unsaturated shear strength characteristics of the investigated soil were determined. Simulation results showed that rainfall duration, instead of intensity, is the crucial factor causing the landslide instability. Results suggest that only about 8 mm of rainfall can infiltrate into the slope during a day. The shear strength component associated with the negative pore-water pressure was found to have a negligible influence on the slope stability at the time of failure since positive pore-water pressure exists along the entire sliding surface. However, it is the unsaturated zone with specific hydraulic features that delay the landslide triggering event. Reduced hydraulic permeability and retention capacity of the soil between the phreatic line and slope surface are factors that postpone build-up of positive pore-water pressure along the sliding surface and enable the slope to remain stable during a long-lasting heavy precipitation.Klizišta uzrokovana oborinama učestalo se događaju diljem svijeta u različitim klimatskim, geološkim i topografskim uvjetima. Rastući broj studija provedenih unazad dva desetljeća ukazuje kako promjene značajki oborina, vezano uz moguće globalne klimatske promjene, mogu dodatno povećati učestalost nastanka klizišta. Uz značajke oborina, karakteristike tla drugi su faktor od krucijalne važnosti za nastanak klizišta uzrokovanih oborinama. Ovisno o odnosu intenziteta kiše i hidrauličkih značajki materijala koji sačinjavaju površinski dio padine, infiltracija oborine u kosinu tijekom vremena odvija se kao nestacionarni proces pri kojem dolazio do promjene vlažnost tla i preraspodjele pornih pritisaka unutar nesaturirane zone geotehničkog presjeka. Pritom najvažniji utjecaj na količinu i brzinu infiltracije, promjenu efektivnih naprezanja i mogući pad čvrstoće materijala imaju hidrauličke i mehaničke značajke tla. Kako bi se riješila jednadžba koja opisuje tečenja vode kroz nesaturirano tlo u vremenu i kvantificirao utjecaj oborine na stanje stabilnosti kosine, potrebno je poznavati funkcije značajki tla u nesaturiranim uvjetima: retencijsku krivulju, funkciju hidrauličke propusnosti te odnos između značajki čvrstoće i vlažnosti tla ili negativnih pornih pritisaka. Matrična sukcija je termin koji se u mehanici nesaturiranih tala najčešće koristi za negativni porni pritisak. Za razliku od plitkih klizišta u materijalima veće propusnosti, studije u kojima se proučava utjecaj nestacionarnog procesa infiltracije oborina na stabilnost dubokih klizišta izgrađenih od materijala relativno niske propusnosti vrlo su rijetke. Prethodna istraživanja klizišta u naslagama fliša u dolini Rječine bavila su se prvenstveno porastom pozitivnih pornih pritisaka uslijed dugotrajnih oborina i utjecajem procesa trošenja flišne stijenske mase na fizičko-mehaničke značajke tla. Pritom je utjecaj dugotrajnih oborina uzet u obzir u analizama stabilnosti jednostavnim podizanje razine podzemne vode (vrlo često i do površine terena), čime se smanjuju efektivna naprezanja i reducira posmična čvrstoća materijala duž klizne plohe. Budući da u ovoj vrsti analiza vrijeme nije jedna od varijabli, distribuciju pornih pritisaka i stabilnost kosine nije moguće analizirati u vremenu. Također, pretpostavlja se da je materijal ispod razine podzemne vode potpuno saturiran, odnosno potpuno suh iznad te razine. Utjecaj matrične sukcije unutar nesaturirane zone geotehničkog presjeka se zanemaruje, kao i svi efekti na hidro-mehaničke značajke tla. Kako bi se, po prvi puta u slučaju istraživanog materijala i predmetnog područja, aplicirali principi nesaturirane mehanike tla na nastanak klizišta uzrokovanih oborinama, provedene su brojne terenske i laboratorijske aktivnosti. Dva osnovna razloga zbog kojih je klizište Valići odabrano kao pilot područje za provedbu istraživanja su prisutnost rezidualnog tla u površinsko dijelu padine za koje je primijećeno značajno isušivanje tijekom sušnih ljetnih mjeseci, te činjenica da su reaktivaciji klizišta u veljači 2014. godine prethodile višemjesečne intenzivne oborine. Neporemećeni uzorci tla uzeti s površinskog dijela klizišta korišteni su za određivanje hidro-mehaničkih značajki tla u nesaturiranim uvjetima. Različitim tehnikama mjerenja i korištenjem ukupno šest laboratorijskih uređaja, određene su retencijske krivulje za proces adsorpcije i desorpcije pri različitim vertikalnim naprezanjima. Metodom nelinearne regresije određeni su parametri najčešće korištenih jednadžbi za opis retencijskih funkcija. Mjerenja hidrauličke propusnosti u saturiranim i nesaturiranim uvjetima, u kombinaciji s retencijskim krivuljama omogućili su definiranje funkcije propusnosti tla u nesaturiranim uvjetima. Time je definirana zavisnost hidrauličke propusnosti materijala od matrične sukcije ili vlažnosti tla. Korištenjem modificiranih uređaja za direktno smicanje tla baziranih na principu translatiranih osi, određen je utjecaj matrične sukcije na značajke čvrstoće tla. Definirane funkcije značajki tla u nesaturiranim uvjetima i rezultati terenskih mjerenja iskorišteni su za definiranje dvodimenzionalnog numeričkog modela kojim je moguće simulirati nestacionarni proces infiltracije oborina u kosinu, te odrediti utjecaj ovog procesa na stanje stabilnosti kosine u vremenu. Kako se parcijalna diferencijalna jednadžba tečenja vode kroz nesaturirano tlo rješava u prostoru i vremenu, pri čemu nelinearnost jednadžbe proizlazi iz nelinearnog odnosa materijalnih značajki i matrične sukcije, rješavanje iste najčešće podrazumijeva iterativne postupke i upotrebu numeričkih metoda. Komercijalno dostupni program SEEP/W (GEO-SLOPE International, Ltd.) baziran na metodi konačnih elemenata korišten je za rješavanje problema infiltracije oborina u kosinu korištenjem realnih ili umjetno generiranih zapisa oborina. Distribucije pornih pritisaka izračunate za različite vremenske trenutke integrirane su u program koji implementira metodu analize granične ravnoteže SLOPE/W (GEO-SLOPE International, Ltd.) kako bi se za svaki od proračunatih profila raspodjele pornih pritisaka izračunao faktor sigurnosti kosine. Time je utvrđena vremenska promjena stanja stabilnosti kosine izgrađene u naslagama fliša, uzimanjem u obzir različitih inicijalnih i rubnih uvjeta. Rezultati analiza potvrdili su dugotrajnost oborina kao presudan faktor za nastanak nestabilnosti, dok ekstremne količine oborina u kraćem vremenskom periodu rezultiraju značajnim površinskim otjecanjem. Čak i kada su mjereni intenziteti u periodu od rujna do veljače 2014. godine reducirani za 50 posto, rezultati analiza ukazuju kako se na dan reaktivacije kosina nalazi u stanju marginalne stabilnosti. Iako komponenta posmične čvrstoće povezana s matričnom sukcijom u trenutku sloma nema utjecaja na stabilnost kosine, utvrđeno je kako upravo nesaturirana zona geotehničkog presjeka, sa svojim specifičnim hidrauličkim značajkama, odgađa gubitak stabilnosti kosine pri ekstremnim oborinama. U tom smislu, smanjena hidraulička propusnost i retencijski kapacitet nestaturirane zone s negativnim pornim pritiscima, faktori su koji usporavaju porast pornih pritisaka duž klizne plohe i osiguravaju stabilnost kosine tijekom dugotrajnih oborina

Rad ne sadrži naslov na drugom jeziku.

Factors primary controlling rainfall-induced slope failures are both rainfall characteristics and soil properties. Rainfall causes a transient infiltration process through the unsaturated part of the slope which affects sloping material by increasing the moisture content and pore-water pressure, changing the effective stress and hydro-mechanical properties of the soil. To study the physical process of rainfall infiltration and how it affects the slope stability state, the dependency between water retention properties, hydraulic permeability, shear strength properties and the water content or negative pore-water pressures existing above the phreatic surface have to be known. Unlike for the shallow-type landslides, very few studies were performed for the case of deep-seated landslides built of material with relatively low hydraulic conductivity. This kind of studies were never performed for landslides occurring in flysch deposits. This study presents the results of different field investigations, laboratory tests, and numerical activities that were performed to build up a numerical model capable to determine the influence of rainfall infiltration process on slope stability state through time. Undisturbed samples of the residual soil from a flysch rock mass were used to perform different laboratory tests in saturated and unsaturated conditions, aimed to provide an advanced hydro-mechanical characterization of the soil behavior under negative pore-water pressure. For the first time, the water retention curves, hydraulic conductivity functions, and unsaturated shear strength characteristics of the investigated soil were determined. Simulation results showed that rainfall duration, instead of intensity, is the crucial factor causing the landslide instability. Results suggest that only about 8 mm of rainfall can infiltrate into the slope during a day. The shear strength component associated with the negative pore-water pressure was found to have a negligible influence on the slope stability at the time of failure since positive pore-water pressure exists along the entire sliding surface. However, it is the unsaturated zone with specific hydraulic features that delay the landslide triggering event. Reduced hydraulic permeability and retention capacity of the soil between the phreatic line and slope surface are factors that postpone build-up of positive pore-water pressure along the sliding surface and enable the slope to remain stable during a long-lasting heavy precipitation.Klizišta uzrokovana oborinama učestalo se događaju diljem svijeta u različitim klimatskim, geološkim i topografskim uvjetima. Rastući broj studija provedenih unazad dva desetljeća ukazuje kako promjene značajki oborina, vezano uz moguće globalne klimatske promjene, mogu dodatno povećati učestalost nastanka klizišta. Uz značajke oborina, karakteristike tla drugi su faktor od krucijalne važnosti za nastanak klizišta uzrokovanih oborinama. Ovisno o odnosu intenziteta kiše i hidrauličkih značajki materijala koji sačinjavaju površinski dio padine, infiltracija oborine u kosinu tijekom vremena odvija se kao nestacionarni proces pri kojem dolazio do promjene vlažnost tla i preraspodjele pornih pritisaka unutar nesaturirane zone geotehničkog presjeka. Pritom najvažniji utjecaj na količinu i brzinu infiltracije, promjenu efektivnih naprezanja i mogući pad čvrstoće materijala imaju hidrauličke i mehaničke značajke tla. Kako bi se riješila jednadžba koja opisuje tečenja vode kroz nesaturirano tlo u vremenu i kvantificirao utjecaj oborine na stanje stabilnosti kosine, potrebno je poznavati funkcije značajki tla u nesaturiranim uvjetima: retencijsku krivulju, funkciju hidrauličke propusnosti te odnos između značajki čvrstoće i vlažnosti tla ili negativnih pornih pritisaka. Matrična sukcija je termin koji se u mehanici nesaturiranih tala najčešće koristi za negativni porni pritisak. Za razliku od plitkih klizišta u materijalima veće propusnosti, studije u kojima se proučava utjecaj nestacionarnog procesa infiltracije oborina na stabilnost dubokih klizišta izgrađenih od materijala relativno niske propusnosti vrlo su rijetke. Prethodna istraživanja klizišta u naslagama fliša u dolini Rječine bavila su se prvenstveno porastom pozitivnih pornih pritisaka uslijed dugotrajnih oborina i utjecajem procesa trošenja flišne stijenske mase na fizičko-mehaničke značajke tla. Pritom je utjecaj dugotrajnih oborina uzet u obzir u analizama stabilnosti jednostavnim podizanje razine podzemne vode (vrlo često i do površine terena), čime se smanjuju efektivna naprezanja i reducira posmična čvrstoća materijala duž klizne plohe. Budući da u ovoj vrsti analiza vrijeme nije jedna od varijabli, distribuciju pornih pritisaka i stabilnost kosine nije moguće analizirati u vremenu. Također, pretpostavlja se da je materijal ispod razine podzemne vode potpuno saturiran, odnosno potpuno suh iznad te razine. Utjecaj matrične sukcije unutar nesaturirane zone geotehničkog presjeka se zanemaruje, kao i svi efekti na hidro-mehaničke značajke tla. Kako bi se, po prvi puta u slučaju istraživanog materijala i predmetnog područja, aplicirali principi nesaturirane mehanike tla na nastanak klizišta uzrokovanih oborinama, provedene su brojne terenske i laboratorijske aktivnosti. Dva osnovna razloga zbog kojih je klizište Valići odabrano kao pilot područje za provedbu istraživanja su prisutnost rezidualnog tla u površinsko dijelu padine za koje je primijećeno značajno isušivanje tijekom sušnih ljetnih mjeseci, te činjenica da su reaktivaciji klizišta u veljači 2014. godine prethodile višemjesečne intenzivne oborine. Neporemećeni uzorci tla uzeti s površinskog dijela klizišta korišteni su za određivanje hidro-mehaničkih značajki tla u nesaturiranim uvjetima. Različitim tehnikama mjerenja i korištenjem ukupno šest laboratorijskih uređaja, određene su retencijske krivulje za proces adsorpcije i desorpcije pri različitim vertikalnim naprezanjima. Metodom nelinearne regresije određeni su parametri najčešće korištenih jednadžbi za opis retencijskih funkcija. Mjerenja hidrauličke propusnosti u saturiranim i nesaturiranim uvjetima, u kombinaciji s retencijskim krivuljama omogućili su definiranje funkcije propusnosti tla u nesaturiranim uvjetima. Time je definirana zavisnost hidrauličke propusnosti materijala od matrične sukcije ili vlažnosti tla. Korištenjem modificiranih uređaja za direktno smicanje tla baziranih na principu translatiranih osi, određen je utjecaj matrične sukcije na značajke čvrstoće tla. Definirane funkcije značajki tla u nesaturiranim uvjetima i rezultati terenskih mjerenja iskorišteni su za definiranje dvodimenzionalnog numeričkog modela kojim je moguće simulirati nestacionarni proces infiltracije oborina u kosinu, te odrediti utjecaj ovog procesa na stanje stabilnosti kosine u vremenu. Kako se parcijalna diferencijalna jednadžba tečenja vode kroz nesaturirano tlo rješava u prostoru i vremenu, pri čemu nelinearnost jednadžbe proizlazi iz nelinearnog odnosa materijalnih značajki i matrične sukcije, rješavanje iste najčešće podrazumijeva iterativne postupke i upotrebu numeričkih metoda. Komercijalno dostupni program SEEP/W (GEO-SLOPE International, Ltd.) baziran na metodi konačnih elemenata korišten je za rješavanje problema infiltracije oborina u kosinu korištenjem realnih ili umjetno generiranih zapisa oborina. Distribucije pornih pritisaka izračunate za različite vremenske trenutke integrirane su u program koji implementira metodu analize granične ravnoteže SLOPE/W (GEO-SLOPE International, Ltd.) kako bi se za svaki od proračunatih profila raspodjele pornih pritisaka izračunao faktor sigurnosti kosine. Time je utvrđena vremenska promjena stanja stabilnosti kosine izgrađene u naslagama fliša, uzimanjem u obzir različitih inicijalnih i rubnih uvjeta. Rezultati analiza potvrdili su dugotrajnost oborina kao presudan faktor za nastanak nestabilnosti, dok ekstremne količine oborina u kraćem vremenskom periodu rezultiraju značajnim površinskim otjecanjem. Čak i kada su mjereni intenziteti u periodu od rujna do veljače 2014. godine reducirani za 50 posto, rezultati analiza ukazuju kako se na dan reaktivacije kosina nalazi u stanju marginalne stabilnosti. Iako komponenta posmične čvrstoće povezana s matričnom sukcijom u trenutku sloma nema utjecaja na stabilnost kosine, utvrđeno je kako upravo nesaturirana zona geotehničkog presjeka, sa svojim specifičnim hidrauličkim značajkama, odgađa gubitak stabilnosti kosine pri ekstremnim oborinama. U tom smislu, smanjena hidraulička propusnost i retencijski kapacitet nestaturirane zone s negativnim pornim pritiscima, faktori su koji usporavaju porast pornih pritisaka duž klizne plohe i osiguravaju stabilnost kosine tijekom dugotrajnih oborina

Strategies of anomalies detection in bridges and tunnels as a tool for structural health management. New approaches and AI support.

L'abstract è presente nell'allegato / the abstract is in the attachmen

Integrated analysis of building vulnerability in urban areas affected by slow-moving, intermittent landslides using SAR Interferometry

Slow-moving landslides are a natural hazard which affects wide areas in the world causing relevant economic damage to structures and infrastructures. To this reason, the analysis of landslide-induced consequences plays a key role in risk prevention and mitigation activities. The thesis shows a general methodology which can be used to forecast spatial and temporal evolution of building vulnerability in urban settlements affected by slow-moving and intermittent landslides. Multi-level and integrated analysis of landslide kinematics and exposed elements allows to assess at different scales of representation and at different levels of accuracy, future conditions of damage of existing facilities. Satellite Radar Interferometry and in particular the Differential SAR Interferometry (DInSAR) technique has been successfully applied as a remote-sensing tool to provide information both on spatial and temporal landslide evolution and on interaction with structures in urban areas. Integration of C and X-band SAR data (acquired between 2002 and 2016) with conventional monitoring techniques allows to reach a thorough knowledge of landslide kinematics; subsequently, structural analyses to detect the relationship between slope movements and building damage have been performed, by using qualitative, semi-quantitative and quantitative approaches. Such methodology has been tested in Moio della Civitella urban settlement, Salerno Province, whose territory is affected by several slow-moving landslides. At small scale of representation, preliminary cause-effect relationship and the updating of landslide inventory map have been provided; at medium scale of analysis, vulnerability zoning map through matrix-approach and influence of vulnerability factors on performance of structures through fragility curves approach, have been defined. Finally, at a detailed scale, structural behavior of buildings has been investigated by means of analytical or numerical analyses. The proposed methodology could be applied to other scenarios affected by similar phenomena and once validated, can be valuably used for damage analysis and forecasting