No description available.

This thesis analyses the governing equation of elastic wave propagation by the finite difference method , and considered absorbing boundary condition and the material damping to simulate behavior of wave propagation. Otherwise, we combined with the mechanics of the soil pore water pressure raised by shear stress effected repeatedly and the soil property is changed by water pressure effected to simulate physical phenomenon in half-space, and probe into the soil liquefaction process during different force types. Using the developed numerical wave propagation model probe into reducing vibration by dug trench and filler trench, and analyzed data by 1/3 octave band method. This thesis discuss with reducing vibration effect by different trench disposed¡Bdifferent filler material property, complex filler, and extending the force source pile length.

Turkey is one of the most earthquake prone countries in the world. The study area, Erbaa, is located in a seismically active fault zone known as North Anatolian Fault Zone (NAFZ). Erbaa is one of the towns of Tokat located in the Middle Black Sea Region. According to the Earthquake zoning map of Turkey, the study area is in the First Degree Earthquake Zone. The city center of Erbaa (Tokat) was previously settled on the left embankment of Kelkit River. After the disastrous 1942 Niksar-Erbaa earthquake (Mw = 7.2), the settlement was moved southwards. From the period of 1900s, several earthquakes occurred in this region and around Erbaa. The 1942 earthquake is the most destructive earthquake in the center of Erbaa settlement. In this study, the geological and geotechnical properties of the study area were investigated by detailed site investigations. The Erbaa settlement is located on alluvial and Pliocene deposits. The Pliocene clay, silt, sand, and gravel layers exist in the southern part of Erbaa. Alluvium in Erbaa region consists of gravelly, sandy, silty, and clayey layers. The alluvial deposits are composed of stratified materials of heterogeneous grain sizes, derived from various geological units in the vicinity. The main objective of this study is to prepare a seismic microzonation map of the study area for urban planning purposes since it is getting more essential to plan new settlements considering safe development strategies after the disastrous earthquakes. In this respect, seismic hazard analyses were performed to deterministically assess the seismic hazard of the study area. Afterwards, the essential ground motions were predicted regarding near fault effects as the study area is settled on an active fault zone. 1-D equivalent linear site response analyses were carried out to evaluate the site effects in the study area. Amplification values obtained from site response analyses reveal that the soil layers in the study area is quite rigid. Furthermore, liquefaction potential and post liquefaction effects including lateral spreading and vertical settlement were also delineated for the study area. The above-mentioned parameters were taken into account in order to prepare a final seismic microzonation map of the study area. The layers were evaluated on the basis of overlay methodologies including Multi-Criteria Decision Analysis (MCDA). Two different MCDA techniques, Simple Additive Weighting (SAW) and Analytical Hierarchical Process (AHP), were carried out in GIS environment. The seismic microzonation maps prepared by SAW and AHP methods are compared to obtain a final seismic microzonation map. Finally, the map derived from the AHP method is proposed to be the final seismic microzonation map of Erbaa. As an overall conclusion, the northwestern part of the study area where the loose alluvial units exist is found to be vulnerable to earthquake-induced deformations. On the other hand, the Pliocene units in the southern and alluvial units in the northeastern part are quite resistant to earthquake effects. In addition, the proposed final seismic microzonation map should be considered by urban planners and policy makers during urban planning projects in Erbaa.

Although silt and clay mixtures were mostly considered to be resistant to cyclic loading due to cohesional components of their shear strength, ground failure case histories compiled from fine grained soil profiles after recent earthquakes (e.g. 1994 Northridge, 1999 Adapazari, 1999 Chi-Chi) revealed that the responses of low plasticity silt and clay mixtures are also critical under cyclic loading. Consequently, understanding the cyclic response of these soils has become a recent challenge in geotechnical earthquake engineering practice. While most of the current attention focuses on the assessment of liquefaction susceptibility of fine-grained soils, it is believed that cyclic strain and strength assessments of silt and clay mixtures need to be also studied as part of complementary critical research components. Inspired by these gaps, a comprehensive laboratory testing program was designed. As part of the laboratory testing program 64 stress-controlled cyclic triaxial tests, 59 static strain-controlled consolidated undrained triaxial tests, 17 oedometer, 196 soil classification tests including sieve analyses, hydrometer, and consistency tests were performed. Additionally 116 cyclic triaxial test results were compiled from available literature. Based on this data probability-based semi-empirical models were developed to assess liquefaction susceptibility and cyclic-induced shear strength loss, cyclically-induced maximum shear, post-cyclic volumetric and residual shear strains of silt and clay mixtures. Performance comparisons of the proposed model alternatives were studied, and it is shown that the proposed models follow an unbiased trend and produce superior predictions of the observed laboratory test response. Superiority of the proposed alternative models was proven by relatively smaller model errors (residuals).

Seismic hazard and microzonation of cities enable to characterize the potential seismic areas that need to be taken into account when designing new structures or retrofitting the existing ones. Study of seismic hazard and preparation of geotechnical microzonation maps will provide an effective solution for city planning and input to earthquake resistant design of structures in an area. Seismic hazard is the study of expected earthquake ground motions at any point on the earth. Microzonation is the process of sub division of region in to number of zones based on the earthquake effects in the local scale. Seismic microzonation is the process of estimating response of soil layers under earthquake excitation and thus the variation of ground motion characteristic on the ground surface. Geotechnical site characterization and assessment of site response during earthquakes is one of the crucial phases of seismic microzonation with respect to ground shaking intensity, attenuation, amplification rating and liquefaction susceptibility. Microzonation mapping of seismic hazards can be expressed in relative or absolute terms, on an urban block-by-block scale, based on local soil conditions (such as soil types) that affect ground shaking levels or vulnerability to soil liquefaction. Such maps would provide general guidelines for integrated planning of cities and in positioning the types of new structures that are most suited to an area, along with information on the relative damage potential of the existing structures in a region. In the present study an attempt has been made to characterize the site and to study the seismic hazard analysis considering the local site effects and to develop microzonation maps for Bangalore. Seismic hazard analysis and microzonation of Bangalore is addressed in this study in three parts: In the first part, estimation of seismic hazard using seismotectonic and geological information. Second part deals about site characterization using geotechnical and shallow geophysical techniques. An area of 220 sq.km, encompassing Bangalore Municipal Corporation has been chosen as the study area in this part of the investigation. There were over 150 lakes, though most of them are dried up due to erosion and encroachments leaving only 64 at present in an area of 220 sq. km and emphasizing the need to study site effects. In the last part, local site effects are assessed by carrying out one-dimensional (1-D) ground response analysis (using the program SHAKE 2000) using both borehole SPT data and shear wave velocity survey data within an area of 220 sq. km. Further, field experiments using microtremor studies have also been carried out (jointly with NGRI) for evaluation of predominant frequency of the soil columns. The same has been assessed using 1-D ground response analysis and compared with microtremor results. Further, Seed and Idriss simplified approach has been adopted to evaluate the liquefaction susceptibility and liquefaction resistance assessment. Microzonation maps have been prepared for Bangalore city covering 220 sq. km area on a scale of 1:20000. Deterministic Seismic Hazard Analysis (DSHA) for Bangalore has been carried out by considering the past earthquakes, assumed subsurface fault rupture lengths and point source synthetic ground motion model. The seismic sources for region have been collected by considering seismotectonic atlas map of India and lineaments identified from satellite remote sensing images. Analysis of lineaments and faults help in understanding the regional seismotectonic activity of the area. Maximum Credible Earthquake (MCE) has been determined by considering the regional seismotectonic activity in about 350 km radius around Bangalore. Earthquake data are collected from United State Geological Survey (USGS), Indian Metrological Department (IMD), New Delhi; Geological Survey of India (GSI) and Amateur Seismic Centre (ASC), National Geophysical Research Institute (NGRI),Hyderabad; Centre for Earth Science Studies (CESS), Akkulam, Kerala; Gauribindanur (GB) Seismic station and other public domain sites. Source magnitude for each source is chosen from the maximum reported past earthquake close to that source and shortest distance from each source to Bangalore is arrived from the newly prepared seismotectonic map of the area. Using these details, and, attenuation relation developed for southern India by Iyengar and Raghukanth (2004), the peak ground acceleration (PGA) has been estimated. A parametric study has been carried out to find fault subsurface rupture length using past earthquake data and Wells and Coppersmith (1994) relation between the subsurface lengths versus earthquake magnitudes. Further seismological model developed by Boore (1983, 2003) SMSIM program has been used to generate synthetic ground motions from vulnerable sources identified in above two methods. From the above three approaches maximum PGA of 0.15g was estimated for Bangalore. This value was obtained for a maximum credible earthquake (MCE) having a moment magnitude of 5.1 from a source of Mandya-Channapatna-Bangalore lineament. Considering this lineament and MCE, a synthetic ground motion has been generated for 850 borehole locations and they are used to prepare PGA map at rock level. The past seismic data has been collected for almost 200 years from different sources such as IMD, BARC (Gauribidanur array), NGRI, CESS, ASC center, USGS, and other public domain data. The seismic data is seen to be homogenous for the last four decades irrespective of the magnitude. Seismic parameters were then evaluated using the data corresponding to the last four decades and also the mixed data (using Kijko’s analysis) for Bangalore region, which are found to be comparable with the earlier reported seismic parameters for south India. The probabilities of distance, magnitude and peak ground acceleration have been evaluated for the six most vulnerable sources using PSHA (Probabilistic Seismic Hazard Analysis). The mean annual rate of exceedance has been calculated for all the six sources at the rock level. The cumulative probability hazard curves have been generated at the bedrock level for peak ground acceleration and spectral acceleration. The spectral acceleration calculation corresponding to a period of 1sec and 5% damping are evaluated. For the design of structures, uniform hazard response spectrum (UHRS) at rock level is developed for the 5% damping corresponding to 10% probability of exceedance in 50 years. The peak ground acceleration (PGA) values corresponding to 10% probability of exceedance in 50 years are comparable to the PGA values obtained in deterministic seismic hazard analysis (DSHA) and higher than Global Seismic Hazard Assessment Program (GSHAP) maps of Bhatia et.al (1997) for the Indian shield area. The 3-D subsurface model with geotechnical data has been generated for site characterization of Bangalore. The base map of Bangalore city (220sq.km) with several layers of information (such as Outer and Administrative boundaries, Contours, Highways, Major roads, Minor roads, Streets, Rail roads, Water bodies, Drains, Landmarks and Borehole locations) has been generated. GIS database for collating and synthesizing geotechnical data available with different sources and 3-dimensional view of soil stratum presenting various geotechnical parameters with depth in appropriate format has been developed. In the context of prediction of reduced level of rock (called as “engineering rock depth” corresponding to about Vs > 700 m/sec) in the subsurface of Bangalore and their spatial variability evaluated using Artificial Neural Network (ANN). Observed SPT ‘N’ values are corrected by applying necessary corrections, which can be used for engineering studies such as site response and liquefaction analysis. Site characterization has also been carried out using measured shear wave velocity with the help of shear wave velocity survey using MASW. MASW (Multichannel Analysis of Surface Wave) is a geophysical method, which generates a shear-wave velocity (Vs) profile (i.e., Vs versus depth) by analyzing Raleigh-type surface waves on a multichannel record. MASW system consisting of 24 channels Geode seismograph with 24 geophones of 4.5 Hz capacity were used in this investigation. The shear wave velocity of Bangalore subsurface soil has been measured and correlation has been developed for shear wave velocity (Vs) with the standard penetration tests (SPT) corrected ‘N’ values. About 58 one-dimensional (1-D) MASW surveys and 20 two-dimensional (2-D) MASW surveys has been carried out with in 220 sq.km Bangalore urban area. Dispersion curves and shear velocity 1-D and 2-D have been evaluated using SurfSeis software. Using 1-dimensional shear wave velocity, the average shear wave velocity of Bangalore soil has been evaluated for depths of 5m, 10m, 15m, 20m, 25m and 30m (Vs30) depths. The sub soil classification has been carried out for local site effect evaluation based on average shear wave velocity of 30m depth (Vs30) of sites using NEHRP (National Earthquake Hazard Research Programme) and IBC (International Building Code) classification. Bangalore falls into site class D type of soil. Mapping clearly indicates that the depth of soil obtained from MASW is closely matching with the soil layers in the bore logs. The measured shear wave velocity at 38 locations close to SPT boreholes, which are used to generate the correlation between the shear wave velocity and corrected ‘N’ values using a power fit. Also, developed relationship between shear wave velocity and corrected ‘N’ values corresponds well with the published relationships of Japan Road Association. Bangalore city, a fast growing urban center, with low to moderate earthquake history and highly altered soil structure (due to large reclamation of land) is been the focus of this work. There were over 150 lakes, though most of them are dried up due to erosion and encroachments leaving only 64 at present in an area of 220 sq km. In the present study, an attempt has been made to assess the site response using geotechnical, geophysical data and field studies. The subsurface profiles of the study area within 220sq.km area was represented by 170 geotechnical bore logs and 58 shear wave velocity profiles obtained by MASW survey. The data from these geotechnical and geophysical technique have been used to study the site response. These soil properties and synthetic ground motions for each borehole locations are further used to study the local site effects by conducting one-dimensional ground response analysis using the program SHAKE2000. The response and amplification spectrum have been evaluated for each layer of borehole location. The natural period of the soil column, peak spectral acceleration and frequency at peak spectral acceleration of each borehole has been evaluated and presented as maps. Predominant frequency obtained from both methods is compared; the correlation between corrected SPT ‘N’ value and low strain shear modulus has been generated. The noise was recorded at 54 different locations in 220sq.km area of Bangalore city using L4-3D short period sensors (CMG3T) equipped with digital data acquisition system. Predominant frequency obtained from ground response studies and microtremor measurement is comparable. To study the liquefaction hazard in Bangalore, the liquefaction hazard assessment has been carried out using standard penetration test (SPT) data and soil properties. Factor of Safety against liquefaction of soil layer has been evaluated based on the simplified procedure of Seed and Idriss (1971) and subsequent revisions of Seed et al (1983, 1985), Youd et al (2001) and Cetin et al (2004). Cyclic Stress Ratio (CSR) resulting from earthquake loading is calculated by considering moment magnitude of 5.1 and amplified peak ground acceleration. Cyclic Resistant Ratio (CRR) is arrived using the corrected SPT ‘N’ values and soil properties. Factor of safety against liquefaction is calculated using stress ratios and accounting necessary magnitude scaling factor for maximum credible earthquake. A simple spread sheet was developed to carryout the calculation for each bore log. The factor of safety against liquefaction is grouped together for the purpose of classification of Bangalore (220 sq. km) area for a liquefaction hazards. Using 2-D base map of Bangalore city, the liquefaction hazard map was prepared using AutoCAD and Arc GIS packages. The results are grouped as four groups for mapping and presented in the form of 2-dimensional maps. Liquefaction possibilities are also assessed conducting laboratory cyclic triaxial test using undisturbed soil samples collected at few locations.

A new reliability-based probabilistic model is developed for the estimation of liquefaction-induced lateral ground spreading, taking into consideration the uncertainties within the model functional form and the descriptive variables as well. The new model is also introduced as performance-based probabilistic engineering tool.

L'objectif de cette thèse est d'étudier la valorisation de la liqueur noire non soufrée par deux procédés hydrothermaux : la gazéification en eau supercritique et la liquéfaction hydrothermale. Ceux-ci seront comparés au procédé actuel de valorisation (évaporation puis combustion dans chaudière Tomlinson) selon 3 critères : le rendement énergétique, la récupération du sodium et la production de molécules aromatiques biosourcées.Lors de la gazéification, il a été montré que la formation de gaz est compétitive à celle de char. Une chauffe rapide et des températures élevées vont favoriser le rendement gaz et donc le rendement énergétique. Cependant les rendements énergétiques sont plus faibles que le procédé actuel car la conversion des composés aromatiques provenant de la lignine est faible dans la gamme de température étudiée. Lors d'un procédé en continu, à plus haute température (700°C) avec une chauffe rapide, le rendement énergétique peut être le double au procédé actuel (simulé à l'équilibre thermodynamique). La préhydrolyse du bois et l'utilisation de bois de résineux vont défavoriser la conversion de la liqueur noire en gaz.La liquéfaction quant-à-elle permet la formation composés phénoliques et d'un biocrude dont la combustion permettant de meilleur rendements énergétique que le procédé actuel. En effet, la lignine de la liqueur noire est hydrolysée en fragments réactifs, pouvant être soit dégradés soit se recombiner pour former le biocrude. Cette dernière est favorisée par la présence des carbohydrates. L'utilisation de bois de feuillus et la préhydrolyse vont améliorer le rendement énergétique.La récupération du sodium est satisfaisante pour les deux procédés, validant la faisabilité de la substitution de la chaudière par ces procédés hydrothermaux. / This thesis aims to study sulfur free black liquor valorization through two hydrothermal processes: supercritical water gasification and hydrothermal liquefaction. These processes will be compared to the industrial process (evaporation and Tomlinson boiler) with 3 mains criteria: energetic yield, sodium recovery and phenolic molecules production.In supercritical conditions, gas formation is competitive with char formation. Fast heating and high temperature permit to increase gas yield, thus energetic yield. However, conversion of phenolic compounds from lignin is low below 500°C, leading to a lower energetic yield than reference. In a continuous process, at high temperatures (700°C) and fast heating, energetic yield should be 2 times higher than industrial process (simulation at thermodynamic equilibrium). Wood prehydrolysis and softwood lead to a lower conversion of black liquor.Hydrothermal liquefaction produces a biocrude which can be burnt and phenolic platform compounds. Indeed, lignin is depolymerized into reactive fragments which can be degraded into platform phenolic molecules. Moreover, the recombination of these fragments, leading to biocrude formation, is favored by the carbohydrates derivatives in black liquor. Wood prehydrolysis and hardwood lead to better energetic and phenolic molecules yields.Sodium recovery is satisfactory for both processes. Substitution of Tomlinson recovery by a hydrothermal process is then possible.

Made available in DSpace on 2015-03-26T13:28:29Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3121914 bytes, checksum: 0c62051de638282573a48ac248e569a2 (MD5) Previous issue date: 2006-08-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work was intended to verify the behavior of a silt sandy tailings sample subjected to dynamic loadings. Shear stress cycles are applied during cyclic triaxial tests over a soil specimen which leads to liquefaction by the increase of generated porepressure. The studies to determine the liquefaction potential of a tailings sample from a typical mining plant was carried out by a series of undrained isotropically consolidated triaxial tests (CKU), of common use for liquefaction potential evaluation of silts and sands, as well as cyclic triaxial tests, which have not yet much used in Brazil although they are recognized around the world by geotechnical community for such liquefaction potential study. Test results obtained from performed tests with static and dynamic loading have shown that the presence of silt somehow inhibited the liquefaction of tested tailings sample. Taking into account the complexity of performing cyclic triaxial tests, the cyclic triaxial device of Civil Engineering Laboratory (LEC/UFV) has proved to be very efficient for tests under dynamic loading, nevertheless test techniques needs some improvements and adaptations concerning testing device and specially regarding specimen preparation. / Este trabalho tem por objetivo analisar o comportamento de um material silto-arenoso quando submetido a carregamentos dinâmicos. Durante o ensaio triaxial cíclico são aplicados ciclos de tensões cisalhantes em uma amostra que elevam os níveis da poro pressão e induz o solo a se liquefazer. Os estudos para determinar o potencial de liquefação de uma mistura de rejeitos de mineração foram realizados ensaios triaxiais do tipo consolidados anisotropicamente não-drenados (CKU), ensaios estes já consagrados no estudo do potencial de liquefação de areias e siltes, e também ensaios triaxiais cíclicos, que apesar de ainda não serem difundidos no Brasil, já tiveram sua eficácia comprovada através de diversos estudos realizados por todo o mundo. Os resulttados obtidos dos ensaios realizados com carregamentos estáticos e cíclicos mostraram que a presença de silte inibiu a liquefação dos rejeitos ensaiados. Considerando a complexidade envolvendo a realização de ensaios triaxiais cíclicos, o equipamento triaxial cíclico do Laboratório de Engenharia Civil (LEC/UFV) mostrou-se eficaz para a realização de ensaios com carregamentos dinâmicos, no entanto a técnica de ensaio necessita certos ajustes tanto no que concerne ao equipamento quanto às técnicas de moldagem de amostras.

Made available in DSpace on 2015-03-13T17:08:23Z (GMT). No. of bitstreams: 1 LucianoFCJ.pdf: 1898824 bytes, checksum: ceb5971b03c32817c3191b8feacf5ac8 (MD5) Previous issue date: 2001-02-21 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This study describes brittle deformation and seismicity in the Castanh?o Dam region, Cear? State, Brazil. This reservoir will include a hidroeletric power plant and will store about 6,7 billions m3 of water. Five main litostratigraphic unit were identified in the region: gneissic-migmatitic basement, metavolcanosedimentary sequence, granitoid plutons of Brasiliano age, Mesozoic basaltic dike swarm, and Cenozoic fluvial terraces of the Jaguaribe river. The region has experienced several faulting events that occurred at different crustal levels. Faults formed at depths less than about 12 km present left-lateral movement and are associated with epidote and quartz infillings. Faults formed at depths less than 7 km are mainly strike-slip present cataclastic rocks, fault breccia and gouge. Both fault groups form mainly NE-trendind lineaments and represent reactivation of ductile shear zones or new formed faults that cut across existing structures. Seismically-induced liquefaction fractures take place in Cenozoic terraces and indicate paleoearthquakes that may have reached at leat 6,8 MS. In short, this work indicate that the level of paleoseismicity is much greater than one observed in the instrumental record. Several faults are favourably oriented for reactivation and induced seismicity should be expected after the Castanh?o Dam impoudment / O presente estudo descreve os aspectos deformacionais fr?geis e a sismicidade na regi?o que ser? inundada pelo reservat?rio do A?ude do Castanh?o, por??o leste do estado do Cear?. O lago artificial ter? a capacidade para armazenar em torno de 6,7 bilh?es de m3 de ?gua. Tamb?m ? planejada a instala??o de uma usina hidroel?trica de pequeno porte. Cinco principais unidades litoestratigr?ficas foram identificadas na regi?o: complexo gn?issico-migmat?tico, seq??ncia metavulcanosedimentar, granit?ides brasilianos, enxame de diques bas?lticos mesoz?icos e terra?os fluviais do Rio Jaguaribe. As falhas indicam a presen?a de sucessivos eventos de reativa??o em n?veis crustais diferentes. As falhas de n?vel crustal profundo (at? 12 km), apresentam uma cinem?tica transcorrente e s?o associadas com preenchimento de ep?doto ou quartzo. As falhas de n?vel crustal intermedi?rio a raso (at? 7 km), s?o principalmente transcorrentes, estando associadas ? cataclasito, brecha e gouge de falha. Ambos os grupos de falhas apresentam um trend principal NE, que pode representar a reativa??o de zonas de cisalhamento d?cteis ou a exist?ncia de eventos fr?geis cenoz?icos. Na ?rea existem v?rias evid?ncias de sismitos, estruturas geol?gicas geradas por paleossismos, em n?veis conglomer?ticos nos Terra?os Fluviais do Rio Jaguaribe, que indicam a ocorr?ncia de sismos com magnitude 6,8 MS, no m?nimo, na regi?o. Assim sendo, a regi?o que ser? inundada do A?ude do Castanh?o, e sua circunvizinhan?a, no decorrer do tempo j? foi atingida por in?meros abalos s?smicos. T?m-se registros hist?ricos, instrumentais e geol?gicos claros destas atividades. Com base nestas informa??es, pode-se afirmar que a regi?o ? predisposta a ser afetada por tremores de terra. Mas isto n?o significa que a obra do A?ude do Castanh?o futuramente poder? ser atingida ou danificada por algum abalo que venha a ocorrer, pois a constru??o est? preparada para resistir, no m?nimo, aos maiores abalos s?smicos j? registrados at? o presente momento na regi?o

La liquéfaction des sols s'observe lors de forts séismes dans des zones saturées en eau et peut causer un enfoncemenl des bâtiments dans le sol. On propose ici un nouveau modèle qui explique de nombreux cas de liquéfaction incompris jusque là. Un modèle analytique de milieu granulaire a été conçu avec une sphère modélisant un bâtiment. Le milieu est soumis à une oscillation horizontale et on caractérise l'état liquéfié par l'amplitude d'enfoncement de la sphère. On suppose que la liquéfaction a lieu lorsque la secousse permet aux grains du milieu de glisser les uns sur les autres. La fenêtre d'accélération permettant ce glissement dépend de la hauteur d'eau dans le milieu, du coefficient de frottement et de la densité du matériau. Les expériences et les simulations numériques réalisées confirment nos prédictions précédentes, caractérisent la micromécanique des milieux liquéfiés, expliquent la vitesse de pénétration de la sphère et ouvrent des pistes pour l'étude des sables mouvants. / Sail liquefaction happens during important earthquakes in water-saturated zones and can make the buildings sink in the soil. A new model explaining many occurences of liquefaction we cannot understand yet is presented in this paper. A new analytical model of granular medium, with a sphere representing a building, has been developed. A horizontal oscillation is applied on the medium. The penetration rate of the sphere then caracterizes the liquefaction state of the modeled soil. We suppose that liquefaction happens when the shaking makes the grains slide against one another. The interval of acceleration allowing this sliding depends on the water height in the medium, on the friction coefficient and on the material density. Experiments and numerical simulations have been carried out. They confirmed our previous predictions, they caracterize the micromecanics of liquefied media, they explain the penetration speed of the sphere and they suggest perspectives to study quicksands.