A indústria mineradora do país sofre constantemente com problemas ambientais devido à qualidade e volume de rejeitos gerados durante o processo de extração do minério. Os volumes gerados demandam grandes áreas para armazenagem e consequentemente obras complexas de contenção dos rejeitos. A engenharia geotécnica busca entender o comportamento mecânico de depósitos destes rejeitos através do uso de ensaios tanto de campo como de laboratório. Para isso utiliza ferramentas e procedimentos consagrados no meio técnico seguindo normas e procedimentos estabelecidos e consagrados mundialmente. No entendimento do comportamento mecânico dos solos argilosos, as análises são desenvolvidas em termos de tensões totais, já para os solos arenosos em termos de tensões efetivas. Todavia, para solos com granulometria intermediária, não se tem um consenso no que se refere à interpretação do comportamento mecânicos a partir de ensaios de campo Este trabalho apresenta resultados de ensaios de DMT e CPTU conduzidos em diferentes velocidades de penetração no intervalo de aproximadamente 1 e 57 mm/s, em depósito de rejeito de mineração, para avaliar tanto a influência da velocidade sobre as medidas do ensaio, quanto a transição das condições de fluxo ao redor do piezocone e durante a expansão da membrana do dilatômetro. Um equipamento simples e de baixo custo foi desenvolvido para monitorar a poropressão no centro da lâmina do DMT e dados são interpretados à luz das condições de drenagem impostas durante a execução do ensaio. Resultados indicam que as leituras e os valores de P0 e P1 são medidas de tensão total e por este motivo influenciadas pela magnitude da poropressão gerada durante a penetração da lâmina. Um novo Fator de Velocidade adimensional “Vt” é proposto para identificar possíveis efeitos de consolidação que ocorrem durante a penetração do piezocone e orientações são dadas para utilização de CPTU e DMT em solos de permeabilidade dentro do intervalo de 10-6 a 10-3 cm/s. / The mining industry of the country constantly suffers from environmental problems due to the quality and volume of waste generated during the mineral extraction process. Volumes generated require large areas for storage and consequently complex works of tailings. The geotechnical engineering seeks to understand the mechanical behavior of deposits of this waste by using assays well as laboratory and field. To this end tools and procedures laid down in the technical means following established rules and procedures consecrated worldwide. In the understanding of the mechanical behavior of clay soils, the analyzes are developed in terms of total stresses and for sandy soils in terms of effective stress. However, in soils with intermediate particle size, there is no consensus concerning the interpretation of the mechanical behavior from field trials. This paper presents the results of DMT and CPTU test conducted at different penetration rates in the range of about 1 to 57 mm / s in mining waste deposit to evaluate both the effect of speed on the measurements of the test, as the transition the flow conditions around the piezocone and during the expansion of the dilatometer membrane. A simple and inexpensive equipment has been developed to monitor the pore pressure in the center of the DMT blade and data are interpreted in the light of the imposed drainage conditions during the test. Results indicate that the readings that the P0 and P1 are total stress measurements and for this reason influenced by the magnitude of pore pressure generated during penetration of DMT blade. A new dimensionless Velocity Factor "Vt" is proposed to identify potential consolidation effects occurring during the penetration of piezocone and guidance is provided for use CPTU and DMT in soil permeability in the range 10-6 to 10-3 cm/s.

Liquefaction is a costly phenomenon where soil shear modulus degrades as the generation of excess pore pressures begins. One of the methods to mitigate liquefaction, is the use of prefabricated vertical drains. Prefabricated vertical drains provide a drainage path to effectively mitigate the generation of pore pressures and aid in shear modulus recovery. The aims of this study were to define shear modulus degradation vs. shear strain as a function of excess pore pressure ratio; define the effects of prefabricated vertical drains on the behavior of pore pressure generation vs. shear strain; and to define volumetric strain as a function of shear strain and excess pore pressure ratios. A large-scale laminar shear box test was conducted and measured on clean sands with prefabricated vertical drains spaced at 3-feet and 4-feet. The resulting test data was analyzed and compared to data without vertical drains. The results show the effect of increasing excess pore pressure ratios on shear modulus and curves where developed to encompass these effects in design with computer programing like SHAKE or DEEPSOIL. The data also suggests that prefabricated vertical drains effectively mitigate excess pore pressure build-up, thus increased the shear strain resistance before pore pressures were generated. Regarding volumetric strain, the results suggests that the primary factor governing the measured settlement is the excess pore pressure ratio. This indicates that if the drains can reduce the excess pore pressure ratio, then the resulting settlement can successfully be reduced during a shaking event. The curves for shear modulus vs. cyclic shear strain as function of pore pressure ratio were developed using data with high strain and small strain which leaves a gap of data in the cyclic shear strain range of 0.0001 to 0.01. Further large-scale testing with appropriate sensitivity is needed to observe the effect excess pore pressure generation on intermediate levels of cyclic shear strain.

Delar av marken i Uppsala består av mäktiga lerlager. Naturliga krypsättningar pågår ständigt i området, en process som i litteraturen benämns geologisk åldring. Ökad belastning i form av uppfyllnad kring byggnader och sänkt grundvattenyta till följd av pumpning av färskvatten bidrar också till sättningar. I ett nybyggt bostadsområde på Kapellgärdet har marksättningarna intill de pålade husen på vissa platser uppgått till 0.3 m på 10 år. Med geotekniska data för området har en jordprofil tolkats. Analys har gjorts utifrån den klassiska sättningsteorin för primärsättningar till av ökade effektivspänningar från fyllnadsmassor och grundvattensänkning. Krypsättningens storlek har uppskattats utifrån erfarenheter vid ett provfält i Stockholm - Mälardalen med liknande jordlagerföljd och geoteknisk egenskaper. De antaganden som görs i den klassiska sättningsmodellen ger en kraftigt förenklad bild av verkligheten, vilket kan leda till stora avvikelser mot det verkliga utfallet. Modellen som används vid beräkning av portrycksutjämningen stämmer inte med verkligheten för den jordlagerföljd som finns på många håll i Stockholm – Mälardalen. Den undre varviga lerans dränerande egenskaper i horisontell riktning och den snabba uttorkningen i den gyttjiga leran kan bidra till det snabba sättningsförloppet. För att bättre kunna förstå sättningsförloppet krävs noggrannare observationer av portrycksutjämningen genom hela leran. Vidare bör bidraget från krypsättningar beaktas, eftersom dessa verkar utgöra en stor del av den totala sättningen. / Parts of the ground in Uppsala consist of thick clay deposits. Natural creep settlements are ongoing in the area due to a process in the literature named geological aging. Increased load on the ground due to fill and lowered groundwater table due to pumping of drinking water are also contributing to settlements. The ground settlements in a new residential area at Kapellgärdet have in parts of the area reached up to 0.3 m during the first 10 years. With geotechnical data from the area, the soil profile has been interpreted. Calculations have been made based on the classic model for primary consolidation caused by increased effective stress from loading and lowered groundwater table. Contribution from creep has been estimated from experience at a test field in Stockholm – Mälardalen with similar soil profile and geotechnical properties. The assumptions made in the classic model provide a simplified picture of the reality, which may lead to large deviations from the actual outcome. The model used in the calculations of pore pressure equalization does not match the reality of the stratigraphy found in many areas in Stockholm – Mälardalen. The drainage properties of the varved clay and the fast desiccation of the muddy clay are thought to contribute to the fast consolidation process. To better understand the consolidation process, more detailed observations of the pore pressure equalization need to be done through the clay. Furthermore, settlement contribution due to creep is needed, as it seems to be a large part of the total settlements.

[pt] Os mecanismos geradores de pressão de poros em subsuperfície têm sido alvo de diversas pesquisas ao longo dos anos. A identificação prévia de zonas de pressão anômalas auxilia na redução do tempo não produtivo (NPT), evitando paralisações, bem como na prevenção de acidentes durante a etapa de perfuração do poço de petróleo. Nesse contexto, este trabalho estuda métodos de previsão de pressão de poros a partir de perfis petrofísicos e de parâmetros de perfuração. Com este objetivo, é apresentada uma revisão bibliográfica abordando tanto os conceitos fundamentais quanto os métodos de previsão de pressão de poros existentes. De modo geral, as estimativas de pressão de poros podem ser divididas em três etapas: (1) antes da perfuração, onde são utilizados perfis petrofísicos de poços de correlação para estimar a pressão de poros; (2) durante a etapa de execução do poço, na qual geralmente são usados os parâmetros de perfuração, além dos eventos de perfuração identificados, e quando disponíveis, as ferramentas de perfilagem em tempo real e dados de pressão; e (3) finalmente na etapa pós-perfuração, onde são utilizados os perfis a cabo, os possíveis perfis de Logging While Drilling (LWD), os eventos de perfuração e os dados de tomadas de pressão na retroanálise. Esses dados são usados para calibrar a pressão de poros estimada previamente para o poço e alimentar a base de dados de poços de petróleo perfurados em uma certa região. Neste trabalho foram realizados estudos de caso, com a realização de estimativas de curvas de pressão de poros, que foram comparadas aos valores de testes de pressão de poços, quando disponíveis. Além dos testes de pressão, também podem ser utilizados eventos indicadores de pressão de poros elevada na calibração, por exemplo o torque, arraste, cavings estilhados ao longo de formações argilosas, influxos em trechos permeáveis, entre outros indicativos. Foi constatado que os gradientes de pressão estimados pelo Método de Bowers apresentam resultados com maior oscilação dos valores quando comparados aos estimados pelo Método de Eaton. A boa aplicabilidade do Método de Eaton é devido ao fato de que na bacia em questão, o mecanismo de subcompactação mostrou-se predominante. Notou-se também que na comparação entre os métodos do expoente d e DEMSE, o resultado do gradiente de pressão de poros obtido através do expoente d está sujeito a menos interferências nas estimativas com relação ao método DEMSE. / [en] The mechanisms that generate pore pressure in subsurface have been the subject of several research over the years. The prior identification of anomalous pressure zones helps to reduce non-productive time (NPT), avoiding stoppages, as well as preventing accidents during the drilling stage of the oil well. In this context, this work studies pore pressure prediction methods from petrophysical profiles and drilling parameters. With this objective, a literature review is presented covering both the fundamental concepts and the existing pore pressure prediction methods. Generally speaking, pore pressure estimates can be divided into three steps: (1) before drilling, where petrophysical profiles from correlation wells are used to estimate pore pressure; (2) during the well execution stage, in which drilling parameters are generally used, in addition to identified drilling events, and when available, real-time logging tools and pressure data; and (3) finally in the post-drilling stage, where the cable profiles, the possible Logging While Drilling (LWD) profiles, the drilling events and the pressure tapping data in the back analysis are used. This data is used to calibrate the previously estimated pore pressure for the well and feed the database of oil wells drilled in a certain region. In this work, case studies were carried out, with estimates of pore pressure curves, which were compared to the values of well pressure tests, when available. In addition to pressure tests, events that indicate high pore pressure can also be used in calibration, for example torque, drag, chipped cavings along clayey formations, inflows in permeable stretches, among other indicators. It was found that the pressure gradients estimated by the Bowers Method shows greater oscillation of the values when compared to those estimated by the Eaton Method. The good applicability of the Eaton Method is related to the subcompaction mechanism predominant in the studied basin. It was also noticed that in the comparison between the Exponent d and DEMSE methods, the result of the pore pressure gradient obtained through the Exponent d is subject to less interference in the estimates in relation to the DEMSE method.

Foundation work can cause damage to adjacent buildings and infrastructure. Drilling is performed in sensitive areas in urban projects and where the ground conditions are difficult. It is important to be aware of the installation effects from drilling. Pneumatic drilling is commonly used in production but hydraulic drilling is advised in sensitive areas. Hydraulic drilling is believed to cause less disturbance in the ground, although there are no available field studies regarding the installation effects induced by water driven drilling.By measuring the pore water pressure and the settlements during the installation of a RD-pile wall the magnitude and extent of the installation effects induced by water powered DTH drilling is investigated in fill material and esker material. The results indicate settlements close to the installed piles in both materials, larger in the esker material. The pore pressure shows both increases and decreases in the esker material, the decreases implies the Venturi effect is present in water driven drilling. The pore water pressure changes are larger at the measurement point furthest away from drilling in the fill material but the settlements are the smallest there. The largest increases of the pore pressure are seen when the hammer flushes water out into the formation and not during drilling. / Grundläggning kan orsaka skador på intilliggande byggnader och infrastruktur. Borrning sker i känsliga områden och i innerstadsprojekt där markförhållandena är svåra. Det är viktigt att vara medveten om omgivningspåverkan borrning av pålar medför. Luftdriven borrning används ofta i produktion men vattendriven borrning rekommenderas i känsliga områden. Vattendriven borrning antas orsaka mindre störningar i marken, även om det inte finns några tillgängliga fältstudier som berör omgivningspåverkan från vattendriven borrning.Genom att mäta porvattentrycket och sättningarna under installationen av en borrad RD-spont undersöks storleken och utbredningen av omgivningspåverkan av vattendriven DTH borrning i fyllnads-material och ås-material. Resultaten indikerar sättningar nära de borrade pålarna i båda materialen, större i ås-materialet. Porstrycket visar både ökningar och minskningar i ås-materialet. Minskningarna antyder att Venturi-effekten är närvarande i vattendriven borrning. Förändringarna i porvattentrycket är större vid mätpunkten längst bort från borrningen i fyllmaterialet, men där är sättningen minst De största ökningarna av porvattentrycket ses när hammaren spolar vatten ut i formationen och inte under borrningen.

For piling works in sensitive soil, especially in inner city projects, it is essential to be aware of the available methods and to choose the most suitable method to minimize the risk of damaging existing buildings or endanger the workers at the construction site. Down-the-hole drilling of piles is a relatively safe method and can be separated into drilling with air powered hammers and water powered hammers. This study compares water powered drilling with air powered drilling and shows that the impact on the soil generated by air powered drilling is larger than that from water powered drilling. A field study was carried out where 4 piles were drilled, two with air powered DTH drilling and two with water powered DTH drilling. The drilling was carried out in clay resting on an approximately 4 m layer of silt and friction soil. The total soil depth was about 12- 15 m. To analyze the soil influence, settlements were measured at ground level and in depth and pore pressure was measured in the middle of the clay layer. This study distinguished two major problems when drilling through this type of soil. The first is the risk of over-drilling in the friction layer. The second problem is the risk of increasing the pore pressure in the clay. Both these problems were experienced when using air powered drilling but for the water powered case only a small pore pressure increase and no over-drilling was observed. In conclusion, drilling with water has less influence on the soil in the sense that it gives a smaller effect on the pore water pressure and causes smaller settlements. / För pålningsarbeten i känsliga jordar och speciellt i innerstadsprojekt är det viktigt att vara medveten om befintliga metoder och välja den mest gynnsamma av dessa för att på så sätt minimera de risker som är sammankopplade med arbetet. Sänkhammarborrning är en relativt säker påldrivningsmetod och kan delas upp i luftdriven borrning och vattendriven borrning. Det här arbetet jämför dessa två metoder och visar att formationspåverkan vid luftdriven borrning är större än den vid vattendriven borrning. Arbetet baseras på en fältstudie där totalt 4 pålar borrades, två med luftdriven borrning och två med vattendriven borrning. Borrningen genomfördes i en formation med lera ovanpå silt och ren friktionsjord och jorddjupet på platsen varierade mellan 12-15 meter. För att undersöka formationspåverkan mättes sättningar på djupet och på markytan och portryck mättes mitt i lerlagret. Arbetet kunde urskilja två huvudsakliga problem vid borrning i den här typen av formation. Det första är risken för överborrning i friktionslager och det andra är risken för portrycksökning i tätare lerlager. Båda dessa fenomen observerades när luftborrning utfördes men inget av dem kunde urskiljas då vattenborrning utfördes. Sammanfattningsvis kan sägas att vattendriven borrning påverkar jorden mindre i den mening att den ger upphov till mindre portrycksökning och orsakar mindre korttidssättningar.

In seismology, an important goal is to attain a better understanding of the earthquake process. In this study of the physics of aftershock generation, I couple statistical analysis with modelling of physical processes in the postseismic period. I present a theoretical formulation for the distribution of interevent times for aftershock sequences obeying the empirically well established Omori law. As opposed to claims by other authors, this work demonstrates that the duration of the time interval between two successive earthquakes cannot be used to identify whether or not they belong to the same aftershock sequence or occur as a result of the same underlying process. This implies that a proper understanding of earthquake interevent time distributions is necessary before conclusions regarding the physics of the earthquake process are drawn. In a discussion of self-organised criticality (SOC) in relation to empirical laws in seismology, I find that Omori's law for aftershocks cannot be used as evidence for the theory of SOC. Instead, I consider that the occurrence of aftershocks in accordance with Omori's law is a result of a physical process that can be modelled and understood. I analyse characteristic features in the spatiotemporal distribution of aftershocks in the south Iceland seismic zone, following the two M6.5 June 2000 earthquakes and a M4.5 earthquake in September, 1999. These features include an initially constant aftershock rate, whose duration is larger following a larger main shock, and a subsequent power law decay that is interrupted by distinct and temporary deviations in terms of rate increases and decreases. Based on pore pressure diffusion modelling, I interpret these features in terms of main shock initiated diffusion processes. I conclude that thorough data analysis and physics-based modelling are essential components in attempts to improve our understanding of processes governing the occurrence of earthquakes.

[pt] Nos últimos 45 anos foram publicados muitos artigos referentes à previsão da pressão de poros em folhelhos, como resultado da necessidade de otimizar o processo construtivo de poços de petróleo. Neste trabalho se apresenta um panorama dos métodos de previsão de pressão de poros existentes, com suas vantagens e desvantagens, com seus pontos fortes e suas críticas, com seus acertos e não acertos; procurando explicar os motivos das diferenças entre o previsto e o real. Em geral são descritos 12 métodos de previsão de pressão de poros, além do conceito do Centróide, 3 técnicas para detectar descarga de tensões efetivas numa formação rochosa, e uma descrição do uso da sísmica na previsão da pressão de poros. Foram aplicados os métodos de Eaton (1975) e Bowers (1995) com o objetivo de fazer uma discussão sobre as incertezas presentes nos parâmetros de cada modelo, complementado o estudo com uma análise de sensibilidade. Como resultado das incertezas existentes se aplicou uma análise probabilística baseada na simulação de Monte Carlo e usando o método de Eaton, com o objetivo de apresentar resultados dentro de intervalos de confiança e permitir planos de contingência durante o projeto de construção do poço. Finalmente são avaliados os resultados de uma análise 3D de previsão de pressão de poros utilizando o modelo de Eaton e o Trend de Bowers. Os cubos de dados foram obtidos por interpolação espacial ponderada partindo de registros de poços. Os resultados mostram que este tipo de análise pode ser usado com fins qualitativos, obtendo cubos de gradientes de pressão de poros aonde se observam as zonas de maior e menor risco. / [en] In the last 45 years were published many articles referring to shale pore pressure prediction, due to the necessity of optimizing the constructive process of petroleum wells. In this work shows up a view of the pore pressure prediction methods with its advantages and disadvantages, with its strong points and its critics, with its hits and failures, trying to explain the causes of the differences between the predicted values and the real ones. As result of the bibliographical revision, we obtained a historical of the pore pressure prediction, furthermore gathering the principal mechanisms of generation of pore pressures and mechanisms of lateral variation of the same. Also, were described 12 methods of pore pressure prediction, the Centroid concept, 3 techniques to detect unloading of effective tensions in a rock formation, and a description of the use of the seismic in the pore pressure prediction. The Eaton (1975) and the Bowers (1995) methods were applied with the objective to discuss the uncertainties in the parameters of each model, this was complemented with sensibility analysis. As result of the existent uncertainties, we applied a probabilistic analyze, based on the Monte Carlo simulation and using the Eaton´s method, with the aim to present results within confidence intervals and to allow contingency plans during the well construction project. Finally, the results of a 3D pore pressure prediction using the Eaton model and the Bowers Trend, were assessed. The data cubes were obtained by weighted space interpolation using well logs at the same basin. We concluded that the results from this type of analysis can be used such as qualitative purposes, obtaining pore pressure gradients cubes, where can be observed bigger and lesser risk zones.

Le Japon s’est doté du réseau sismologique à haute sensibilité (Hi-net) qui contient plus de 1000 stations permanentes, qui fournissent d’immenses ensembles des données continues au Japon. Dans le cadre d’un accord avec le NIED, nous bénéficions d’enregis- trements de fond de données à court et à long periodes pour analyser les variations de vitesse sismiques, afin de suivre l’évolution mécanique de la croûte temporelle avec une résolution temporelle mensuelle à quotidienne dans les différentes bandes de périodes. Les résultats de courte période nous aident à mieux comprendre la sismologie environnemen- tale sur les processus souterrains sous les impacts de certains forçages environnementaux environnants tels que l’hydrologie, la thermoelasticité et certains effets de charge directe. Les résultats de longues périodes montrent des réponses co- et post-sismiques différentes avec la profondeur. Il s’agit d’une méthode supplémentaire et directe pour révéler en profondeur le champ de contrainte/déformation, ce qui améliore la perception du mécanisme d’un tremblement de terre. Cette thèse comprend principalement les trois parties suivantes.La première partie est consacrée à la présentation de la relation entre la fonction de Green et les corrélations croisées. La simulation numérique à Hokkaido vérifie également l’établissement de la relation entre les deux.La seconde partie concerne l’analyse des variations transitoires de la vitesse des ondes sismiques dans la croûte provoquées par les perturbations environnementales. Les impacts des perturbations saisonnières environnementales sur la déformation de la croûte sont généralement suivis et discutés en fonction des observations géodésiques. Récemment, la surveillance du bruit sismique ambiant fournit de nouvelles informations sur la déformation continue de la croûte, révélée par les changements de vitesse sismiques temporels. Dans cette étude, nous identifions les différents facteurs environnementaux responsables des effets saisonniers locaux et montrons comment une meilleure compréhension de ces perturbations de la croûte causée par l’environnement améliore les observations des modifications des propriétés sismiques induites par la tectonique.La dernière partie consiste à étudier la réponse mécanique de la croûte aux grands séismes. La surveillance de la vitesse sismique basée sur le bruit peut directement son- der en permanence l’état mécanique de la croûte en profondeur. Dans ce travail, nous étudions la réponse de la croûte terrestre au séisme de Tohoku-oki Mw 9.0, 2011. Nous employons ici pour la première fois le réseau très dense de Hi-Net tiltmètre en tant que sismomètres de longue période (8 - 50 s) pour que la surveillance basée sur le bruit échantillonne la croûte à plus de 5 km en profondeur. L’évolution spatio-temporelle des changements de vitesse sismiques dans différentes bandes de périodes révèle une réponse sismique dépendant de la profondeur, qui est la limite pour les données des sismomètres courte période. Le résultat pourrait avoir des implications à la fois sur la réponse viscoélastique de la croûte aux grands déformations ou sur une réponse complexe des vitesses sismiques de la croûte à un ècoulement de fluide transitoire.Cette thèse s’inscrit dans le cadre d’une collaboration plus générale entre ISTerre- Universit Grenoble Aples et le Massachusetts Institute of Technology visant à développer des outils de surveillance dans des contextes naturels et industriels. / The Japanese High Sensitivity Seismograph Network (Hi-net) contains more than 1000 permanent stations, which provide large continuous data sets throughout Japan. In the framework of an agreement with NIED, we benefit from both short period and tilt meters data downhole recordings to analyze the seismic velocity variations, thus to follow the mechanical evolution of the crust in different time scales with a temporal re- solution from monthly to daily in different period ranges. The short period results help us better understanding the environmental seismology on the subsurface processes under the impacts of some surrounding environmental forcing such as hydrology, thermoelas- ticity, and some direct loading effects. The results from long periods show different co- and postseismic responses with depth. This is a supplementary and direct method to disclose the stress/strain field at depth improving the perception of the mechanism of an earthquake. This thesis mainly consists of the following three parts.The first part is devoted to the theoretical demonstration of the relationship between the Green’s function and cross-correlations. The numerical simulation in Hokkaido also verifies the establishment of the in-between connection.The second part is about the analysis of the transient changes of seismic wave velo- city in the crust caused by environmental perturbations. The impacts of environmental seasonal disturbances to crustal deformation are usually tracked and discussed based on geodetic observations. Recently, ambient seismic noise-based monitoring provides new insights into the continuous deformation in the crust as revealed by the temporal seismic velocity changes. In this study, we identify the different environmental factors in charge of the local seasonal effects and show how better understanding these environmentally induced crustal perturbations improves the observations of tectonic-induced seismic pro- perty changes.The last part is to study the mechanical response of the crust to large earthquakes.Noise-based seismic velocity monitoring can directly probe the mechanical state of the crust at depth continuously in time. In this work, we study the response of the crust to the Mw 9.0, 2011 Tohoku-oki earthquake. we employ here for the first time the very dense network of Hi-net tilt meters as long period (8 – 50 s) seismometers for the noise-based monitoring to sample the crust below 5 km depth. Spatio-temporal evolution of seismic velocity changes in different period bands reveals depth-dependent seismic response. The result could have implications of both nonelastic response of the crust to large strain changes or a complex response of crustal seismic velocities to transient fluid flow.This thesis is in the context of a more general collaboration between ISTerre- Universit Grenoble Aples, and the Massachusetts Institute of Technology aiming at developing tools for monitoring in natural and industrial contexts.

O conhecimento de zonas potencialmente instáveis no fundo do mar é de fundamental importância para o desenvolvimento das estruturas marinhas, pois permite posicionar estruturas offshore em áreas mais seguras, reduzindo-se possíveis danos, custos e eventual poluição ambiental. Nesse contexto, o objetivo do presente trabalho é investigar, através de uma abordagem analítico-numérica, a estabilidade de maciços submarinos submetidos ao carregamento cíclico da onda. O efeito das ondas de água sobre o leito submerso é descrito pela propagação de uma onda de pressão ao longo de sua superfície, empregando-se a teoria linear de Stokes. São considerados maciços com superfície superior horizontal e inclinada, constituídos por material coesivo (argilas) e material granular (areias). Em maciços constituídos por solos finos, a capacidade resistente do material é modelada pelo critério de Tresca não-homogêneo e a análise da estabilidade é desenvolvida em condição não drenada. Por outro lado, em leitos granulares, a resistência do meio depende explicitamente do valor da poropressão, sendo descrita classicamente pelo critério de Coulomb sem coesão. A análise de estabilidade é então desenvolvida em tensões efetivas e o gradiente de poropressão atua como uma força volumétrica sobre o esqueleto, caracterizando o modo de carregamento principal deste material. Em razão da tendência a se densificar quando submetido a um estado de tensões desviadoras cíclicas, ocorre, em geral, a acumulação de excesso de poropressão no maciço granular. Consequentemente, o acoplamento entre o comportamento do material e o carregamento cíclico tem fundamental importância sobre o cálculo do excesso de poropressão desenvolvido. Para determinação das forças de percolação, considera-se uma abordagem simplificada baseada na partição das deformações em contribuições reversível e irreversível, que permite desacoplar o cálculo da pressão intersticial induzida pela onda. Aplicando-se conceitos da teoria da Análise Limite é possível formular limites inferiores e superiores da máxima amplitude segura do carregamento da onda. Finalmente, os efeitos da declividade da superfície do leito e da espessura de camada de solo sobre a estabilidade são analisados. / The knowledge of potentially unstable areas on the seabed is of fundamental importance to the development of marine structures, because it allows to install offshore structures in safer areas, reducing possible damages, costs and eventual environmental pollution. In this context, the objective of the present work is to investigate the stability of submarine soil masses subjected to the wave cyclic loading through analytical-numerical approaches. The effect of water waves on the submerged bed is described by the propagation of a pressure wave along its surface, using the Stokes’s linear theory. Soil masses with horizontal and sloped upper surface, composed of cohesive material (clays) and granular materiais (sands) are considered in this study. In soil masses constituted of fine soil, the material strength capacity is modeled by the non-homogeneous Tresca criterion and the stability analysis is carried out in undrained condition. On the other hand, in granular beds, the strength explicitly depends on the pore pressure value, being classically described by the Coulomb criterion without cohesion. Then, the stability analysis is developed in effective stress and the pore pressure gradient acts as a volumetric force on the skeleton, characterizing the main charging mode of this material. Due to the tendency to densify when subjected to a cyclic deviatoric stress state occurs, in general, the build-up of pore pressure excess in the granular mass. Consequently, the coupling between the material behavior and the cyclic loading has fundamental importance in the calculation of the pore pressure excess generated. In order to define the seepage forces, a simplified approach based on the partition of deformations in reversible and irreversible contributions is considered, which allows to decouple the wave-induced pore pressure calculation. Applying the concepts of the limit analysis theory it is possible to formulate upper and lower boundaries of the maximum safe amplitude of the wave loading. Finally, the effects of the seabed surface steepness and of the soil layer thickness on the stability are analyzed.