Due to the COVID-19 pandemic, disposable face-masks were excessively used around the world, which led to severe environmental problems. The main purpose of this research is to test the possibility of reinforcing a sandy soil with mask fibers to reuse pandemic-generated waste materials. When testing the compaction properties, the sand was reinforced with a fiber content that increased from 0% to 0.5%, with successive small increments of 0.1%. An optimum content of 0.1% remarkably increased the maximum dry density of the soil and dropped its optimum moisture content. Add to that, it was noticed that 15 mm and rectangular chips were respectively the optimum fiber length and shape to maximize the improvement of the sand compaction properties. Regarding the shear strength, fiber contents of 0.1%, 0.25%, and 0.5% were adopted. The direct shear tests have shown that the highest enhancement was observed for an optimum fiber content of 0.25%. Similarly to compaction tests, 15 mm and rectangular chips were respectively the optimum fiber length and shape to extremely enhance the shear resistance of the tested sand.

The potential of liquefaction is evaluated by calculating the reliability index using the first order reliability method (FORM). The probability of liquefaction is then obtained from the reliability index. Two models (the recommended by the NCEER and the one proposed by Boulanger and Idriss) are used to define the limit state function for liquefaction triggering analysis. These models are based on deterministic methods considering SPT tests. The statistical characteristics of the model uncertainty of Boulanger and Idriss model are determined through an extensive reliability analysis using Bayesian mapping function calibrated with a set of quality case histories. Soil from Lebanon corresponding to a site located at the North of Beirut where SPT tests have been carried out is used for comparative analysis between the two models. The impact of the coefficient of variation of the input variables on the probability of liquefaction is examined.

Based on in situ tests results, the deterministic approaches express the soil liquefaction potential in terms of safety factor and the probabilistic approaches define it in terms of probability of liquefaction. The developed methods for soil liquefaction evaluation predict the behavior of a soil element. However, the liquefaction potential index (LPI) evaluates the performance of the entire soil column and allows a measurement of the severity of liquefaction. In this paper, the liquefaction potential is used in conjunction with deterministic approach and reliability based probabilistic approach using SPT and CPT results. A site located to the north of Beirut where the soil investigation consisted of a total of sixteen boreholes with continuous coring and standard penetration test every 1.5 m of depth and thirty-three boreholes with cone penetration test is subjected to liquefaction potential study. Liquefaction potential index (LPI) is calculated at each borehole location from the obtained safety factor or the calculated probability of liquefaction. Spatial distribution of soil liquefaction potential is presented in form of contours maps of the (LPI) values for each considered method. The results show that the evaluation of LPI using the reliability based probabilistic approach and the CPT results is a more conservative method giving larger area with LPI values higher than 15.

Lebanon is situated on the 1000 km long Levant transform fault that separates the Arabic from the African tectonic plates. In Lebanon, the Levant fault splits up into a set of ramifications that had, in the past, generated major destructive earthquakes causing a lot of destruction and thousands of casualties. The most devastating one was the 551 A.D. offshore earthquake that destroyed Beirut, the capital of Lebanon. This paper presents a site effect study in Beirut, aimed at proposing a framework for future microzonation works in the city. It includes two complementary parts. A 6-month, temporary seismological experiment was first conducted to estimate the site response at 10 sites sampling the main geological units of Beirut on the basis of local and regional earthquake recordings. This spatially sparse information was then complemented by a large number (615) of microtremor measurements covering the Beirut municipality and part of its suburbs with a 400 m dense grid. The recordings were analysed with the standard site-to-reference and horizontal-to-vertical spectral ratio methods for earthquake recordings, and the horizontal-to-vertical ratio for ambient noise recordings. Significant ground motion amplification effects (up to a factor of 8) are found in a few areas corresponding to recent deposits. The consistency between results from earthquake and microtremor recordings allows proposing a map of the resonance frequencies within the city and its suburbs, with frequencies ranging from 0.5 to 5 Hz for the deepest deposits, and 5–10 Hz for shallow areas. Finally, the results are discussed and a way to combine the results obtained from the temporary stations to the great number of recordings coming from the permanent Lebanese network is proposed.

The interpretation of five 2D PSTM seismic reflection sections (14 s TWT) covering the northern Levant Basin revealed a total of 10 horizons, among which, one is interpreted as an interface that may represent the Moho. The interpretation of seismic packages and their bounding surfaces as well as the seismic facies analysis were constrained by published 2D seismic interpretations of the northern Lebanese offshore. A total of nine seismic packages are identified in the basin with ages varying from the Mid Jurassic to the Quaternary. The filling of the basin is made up of thick Cenozoic and Mesozoic strata deposited above rifted Triassic - Early Jurassic interval. The sediments are deposited in deep water mixed-settings resulting from high-stand systems (various types of carbonate platforms) and low-stand systems (siliciclastic and carbonate deep-water turbidite complexes). Carbonate and siliciclastic systems are sealed by 1-1.5 km of evaporites, and underlie Plio-Quaternary hemipelagic and pelagic sediments intercalated by turbiditic sheets. The time horizons were converted into depth using two methods; the first one is based on stacking velocities and the second one on velocities resulting from refraction data. 2D crustal modeling was achieved by integrating free-air gravity anomaly, geoid heights and topography data on the five interpreted PSTM seismic lines. The models representing five sections across the northern Levant Basin, show a progressively attenuated crystalline crust in an EW direction (away from the basin's eastern margin). The crystalline crust is best interpreted as a strongly thinned continental crust under the Levant Basin, represented by two distinct components, an upper and a lower continental crust. The Moho appears to be situated between 20 and 23 km in the central and southern Lebanese offshore. Estimated surface heatflow in the basin is around 40 mW/m(2), which is lower than reported values for the onshore and the margin. These differences in heatflow values between the offshore, the margin and the onshore have an important impact on hydrocarbon maturation and assessment of potential petroleum systems.

The paper analyses the evaluation of the liquefaction potential based on in situ tests.The four studied methods are those recommended by the NCEER and those proposed by Boulanger and Idriss.These methods are based on the cyclic stress approach, which characterizes both earthquake loading and soil liquefaction resistance in terms of cyclic stresses.Liquefaction resistance is based on two field tests results, namely SPT and CPT.An extensive analysis is carried out to understand and compare the results obtained.The factor of safety against liquefaction is discussed in terms of many parameters particularly the depth, the percentage of fines and the number of blows N. The analyzed case study is a site in Qatar.Hundreds of CPT and SPT were performed at this site where the foundation soil is calcareous sand, this kind of soil being not commonly considered in the literature.As far as factors of safety against liquefaction are concerned, the results are very close in general, and correspond to the geological and geotechnical soil profile.Analysis shows that the CPT Boulanger and Idriss method is the most conservative.The case study wants to contribute to the understanding of the factors that influence the cyclic stress approach.The SPT resistance is most commonly used but the CPT resistance approach must be gaining more fields in future earthquake geotechnical engineering projects.

This paper discusses the deep structure of the lithosphere underlying the easternmost Mediterranean region, in particular the Levant Basin and its margins, where the nature of the crust, continental versus oceanic, remains debated. Crustal thickness and the depth of the lithosphere-asthenosphere boundary (LAB) as well as the crustal density distribution were calculated by integrating surface heat flow data, free-air gravity anomaly, geoid and topography. Accordingly, two-dimensional, lithospheric models of the study area are discussed, demonstrating the presence of a progressively attenuated crystalline crust from E to W (average thickness from 35 to 8 km). The crystalline crust is best interpreted as a strongly thinned continental crust under the Levant Basin, represented by two distinct components, an upper and a lower crust. Further to the west, the Herodotus Basin is believed to be underlain by an oceanic crust, with a thickness between 6 and 10 km. The Moho under the Arabian Plate is 35–40 km deep and becomes shallower towards the Mediterranean coast. It appears to be situated at depths ranging between 20 and 23 km below the Levant Basin and 26 km beneath the Herodotus Basin, based on our proposed models. At the Levantine margin, the thinning of the crust in the transitional domain between the onshore and the offshore is gradual, indicating successive extensional regimes that did not reach the beak up stage. In addition, the depth to LAB is around 120 km under the Arabian and the Eurasian Plates, 150 km under the Levant Basin, and it plunges to 180 km under the Herodotus Basin. This study shows that detailed 2D lithosphere modeling using integrated geophysical data can help understand the mechanisms responsible for the modelled lithospheric architecture when constrained with geological findings.

This work aims to be an initial investigation to the use of geophysical and limited geotechnical data to obtain soil and stratigraphy characterization. This approach is essential for developing countries where geotechnical data is typically scarce and expensive. This type of consolidation was used on a study area in Lebanon that consists of a failed slope. A consolidation of data from surface wave measurements, electrical resistivity, and in-situ data was carried out where each gave a part of the description of the site. The surface wave measurements revealed that the seismic bedrock depth was not reached in the range of measurements carried out for this study. Soil was revealed to be mostly clayey sand. Geostatistical analysis results showed that spatial variability of soil properties in both vertical and horizontal directions could be achieved from the electrical resistivity measurements. For this study area, it was shown that 9 m and 4 m were the sizes of the essential spatial structures in the data in the horizontal and vertical directions respectively. Another finding of interest was a second order trend in the resistivity data in both the horizontal and vertical directions that can be due to the decrease in resistivity with depth due to soil compression. All in all, the slope has been better understood with the merging of data and the aspects that require further investigation have been clearly depicted.

Researchers and Engineers are currently attempting to remediate earth dams to prevent damaging effects of potential seismic loading. The actual state of knowledge needs to be improved at least in the two following fields: soil properties and seismic response calculation techniques. Moreover, the effect of earthquake acceleration on the response of the dam needs to be further understood especially as far as amplification effects are concerned. In this paper, the assessment of the failure is given both from geotechnical as well seismic points of view. A comprehensive parametric study covering the effects of soil cohesion and soil friction angle on the values of yield accelerations is carried out. A dynamic factor of safety has been established as a function of earthquake acceleration. Furthermore, the outcomes on crest response spectra of input earthquake acceleration, soil shear wave velocity, and reduction of soil small strain shear modulus Gmax with induced deformations is deeply analyzed. Results are promising and will be a contribution to the geotechnical earthquake dam engineering domain.

Landslide effects have been numerous on infrastructures and on human lives, and their consequences during an earthquake might be a disaster. The pan Arab highway is a project comprising a network of roads binding the Middle East countries together. In the Lebanese mountains, in the Dahr el Baidar area and over the past twenty years, many slope instabilities and failures caused great damages in the highway projected area and other surrounding roads. This region is much known for its tectonic activity due to the fact that it is limited in the east by the major fault of Yammouneh, extension of the Dead Sea fault that crosses the Middle East, and by many minor faults in the west. Hundreds of boreholes have been executed and many geotechnical studies show that rain as well as presence of poor soil are two main causes of these landslides in the area. The purpose of this research work is to evaluate how a slope will behave under seismic loading, and how the factor of safety and the slip circle will vary during an earthquake, with a special attention given to the role of dynamic soil properties in understanding slope instabilities. First, it has been proven that the amplification period and the amplification value itself at surface depend on the dynamic properties of the soil profile. Indeed, the amplification varies differently with a change in the maximum shear modulus, shear modulus reduction curve and damping curve. In addition, increasing the shear modulus and reducing the damping would lower the amplification values at surface. Furthermore, this study showed that, while increasing the parameters of a single soil layer at surface, the slip circle will move to a different layer with weaker properties. Moreover, while increasing the parameters of soil layers in depth – in other words while increasing the stiffness contrast between surface and deep layers – the displacement of slip circle will not be observed, but the factor of safety will be reduced by 55% in some cases. It is interesting to see how amplification of acceleration in time domain will depend on mechanical and dynamic proprieties of the soil, whereas amplification of RRS in frequency domain will only depend on the layer height above rock and the rock’s acceleration response spectrum.

The slope of Dahr El Baidar located on the central mountain of Lebanon hosts a section of the Arab Highway that is under construction to connect Beirut to neighboring Arab countries. This slope has experienced several failures; yet most involved geotechnical companies have investigated the slope with classical geotechnical procedures. In this paper, the analysis of the slope is performed using an integrated geo-assessment approach to identify the principal causes of failure and understand its dynamic behavior. The study includes geological, geophysical and geotechnical soil characterization of the designated area. The geological analysis reveals the presence of faults in the vicinity, in addition to a layer of weak clay at the surface. The geotechnical investigation is based on the interpretation of several boreholes. Geophysical tests are performed using ambient noise vibration technique in order to reveal the resonant frequency and thickness of the soil deposit material. A correlation between geotechnical and geophysical tests was used to establish soil properties in the studies. The above data is used towards a better understanding of the cause and occurrence of the failing zone. A dynamic analysis is conducted to determine the slope amplification and compare the simulated frequencies with the measured ones.

Earthquake-induced ground shaking is one of the most recurrent causes of slope instabilities that might be leading to landslides. In the present research, a representative clayey slope is analyzed. Empirical methods such as the Newmark method and Makdisi Seed method are considered for the determination of the maximum deformation in a slope under dynamic loading. Stress deformation methods using finite element techniques are also used to estimate slope deformations under the same conditions. A relation is established between the yield acceleration, the cohesion of soil, and the slope angle. Then, the evolution of the dynamic factor of safety is analyzed in terms of the yield acceleration of the slope. A procedure is developed to establish a relation between slope deformation and dynamic factor of safety. Curves linking the factor of safety to yield acceleration are established for different values of cohesion and friction angle of soil.

In order to retrieve quantitative information on soil deposits characteristics for better understanding site amplification observed in Great Beirut (Brax, 2013), active and passive surface wave measurements were acquired at various sites sampling the main geological units. Besides, more than 40 geotechnical soil reports containing Standard Penetration blow counts (N-SPT) around the city and the surbubs were collected, some being very close to the geophysical measurements location. Geotechnical boreholes outline the presence of a soft clay layer of varying thickness embedded in coarser formation (gravel, sand) in the Quaternary alluvium plain of Beirut, while alternance of clayey sand, sand and silty sand dominates in the Quaternary sandy cover. Surface-wave dispersion estimates were inverted by introducing the a priori knowledge from borehole logs and N-SPT profile in the ground model parameterization. Inverted shear-wave velocity profiles (Vs) indicate shear-wave velocity at the surface between 150 and 300 m/s whatever the site location. Limestone bedrock depth is largely variable, from 25 to 160 m, depending on site location. N-SPT values and corresponding Vs estimates derived for sand and clay formation are consistent with empirical relationships found in litterature. However, additional geotechnical profiles and/or geophysical measurements are required to enable deriving robust specific Vs-N relationship for Beirut soils. 1 PhD, University Grenobles Alpes/CNRS/IRD, ISTerre, F-38000 Grenoble, Grenoble, France, cecile.cornou@ujf-grenoble.fr 2 PhD, Centre de Recherches Géophysique, CNRSL, Lebanon, brax@cnrs.edu.lb 3 PhD student, University Grenobles Alpes/CNRS/IRD, ISTerre, F-38000 Grenoble, Grenoble, France, nancy.salloum@ujf-grenoble.fr 4 Professor, Saint Joseph University, Beirut, Lebanon, muhsin.rahal@usj.edu.lb 5 Master student, Saint Joseph University, Beirut, Lebanon, farah.harakeh@hotmail.com 6 Professor and Chair, Notre Dame University-Louaizé, Lebanon, jharb@ndu.edu.lb 7 Assistant Professor, Notre Dame University-Louaizé, Lebanon, dabdelmassih@ndu.edu.lb 8 Eng., ISTerre, Grenoble University, Grenoble, France, armand.mariscal@ujf-grenoble.fr 9 PhD, ISTerre, Grenoble University, Grenoble, France, denis.jongmans@ujf-grenoble.fr 10 PhD, ISTerre, Grenoble University, Grenoble, France, christophe.voisin@ujf-grenoble.fr 11 PhD, ISTerre, Grenoble University, Grenoble, France, pierre-yves.bard@ujf-grenoble.fr

Simplified methods based on in-situ tests such as the standard penetration test (SPT) and the cone penetration test (CPT), are widely used by geotechnical engineers for assessing the liquefaction potential of soils. The four studied methods are those recommended by the NCEER and those proposed by Boulanger and Idriss. In our study, a reliability analysis, based on conventional probability theory, is used to calculate the relationship between the liquefaction probability and reliability index on one hand, and the traditional factor of safety on the other hand. The case study is in Qatar in the Persian Gulf. Hundreds of CPT and SPT tests have been carried out at this site. Uncertainty in the evaluation of peak horizontal earthquake induced ground acceleration is considered. It is observed that the probability of liquefaction drastically changes for a small change in the factor safety. RÉSUMÉ Des méthodes simplifiées basées sur les essais in-situ comme l’essai de pénétration standard (SPT) et l’essai de pénétration au cône statique (CPT), sont très utilisées par les ingénieurs géotechniciens pour l’évaluation du potentiel de liquéfaction de sols. Les quatre méthodes étudiées sont celles recommandées par le NCEER et celles proposées par Boulanger et Idriss. Dans notre étude, une analyse fiabiliste basée sur la théorie de probabilité conventionnelle est utilisée pour établir la relation entre la probabilité de liquéfaction et l’indice de fiabilité d’une part, et le coefficient traditionnel de sécurité d’autre part. L’étude de cas se trouve au Qatar dans le golfe persique. Des centaines d’essais SPT et CPT ont été réalisés. L’incertitude dans l’évaluation de l’accélération horizontale maximale induite est considérée. Il est observé que la probabilité de liquéfaction est modifiée significativement pour un léger changement du coefficient de sécurité.

Cyclic shear strain plays a key role in the determination of soil behavior in geotechnical earthquake engineering. The aim of this research is to explain the context of threshold strain that delimits a transition state between small and large deformations. Two methods were used to model the degradation of shear modulus against shear strain: best fit line and best fit curve. A good agreement was observed between experimental results and modeled curves.

Earthquake induced ground shaking is one of the most recurrent causes of slope instabilities that might be leading to landslides. In the present research, a typical clayey slope is analysed. Empirical methods such as Newmark method, and Makdisi Seed method, are considered for the determination of the maximum deformation in a slope under dynamic loading. Stress deformation methods using finite element techniques are also used to estimate slope deformations under same conditions. A relation is established between the yield acceleration, the cohesion of soil and the slope angle. Then, the evolution of the dynamic factor of safety is analysed in terms of the yield acceleration of the slope. A procedure is developed to establish a relation between slope deformation and dynamic factor of safety. Curves linking the factor of safety to yield acceleration are established for different values of cohesion and friction angle of soil. RÉSUMÉ Les mouvements du sol induits par les séismes sont une cause récurrente des instabilités d’une pente, pouvant mener à des glissements de terrains. Dans ce travail, une pente argileuse typique est considérée. Des méthodes empiriques, comme les méthodes de Newmark et Makdisi Seed, sont utilisées pour la détermination de la déformation maximale de la pente sous sollicitations sismiques. Les méthodes contraintesdéformations basées sur les éléments finis sont utilisées pour estimer les déformations de la pente dans des conditions similaires. Une relation est établie entre l’accélération de ruine, la cohésion du sol et l’angle de la pente. L’évolution du facteur de sécurité dynamique est aussi analysée en termes de l’accélération de ruine. Une procédure est développée pour établir une relation entre les déformations calculées et le facteur de sécurité dynamique. Des courbes reliant le facteur de sécurité à l’accélération de ruine sont tracées pour différentes valeurs des paramètres mécaniques.