Publications

Le phénomène de liquéfaction concerne certaines formations géologiques définies par leur nature (sables, limons,vases), granulométrie (uniforme, de 0,05 à 2 mm) ; cohésion (plasticité faible), densité (lâche et moyenne) et degré desaturation (saturée). Généralement ce phénomène a lieu dans des sols sableux non cohésifs et saturés ; mais aussi dansdes sables moyennement grossiers, des limons alluvionnaires, des cendres, des résidus miniers… qui peuvent formerdes dépôts peu denses et instables, particulièrement si ceux-ci présentent une granulométrie uniforme et des particulesde forme arrondies. La liquéfaction se produit principalement dans les sols proches de la surface (z < 15m) et rarementdans des couches plus profondes. La plupart des cas recensés dans la littérature concernent les 10 premiers mètres deprofondeur.

During the Petrinja earthquake sequence in December 2020, numerous liquefied sandejections came to the surface along the Kupa, Sava and Glina rivers in Quaternary alluvialsediments. In October 2022, we performed field investigation in the epicentral area, involvinggeotechnical and geophysical techniques, at different sites with sand ejecta or lateralspreading along the Kupa river. Geotechnical soundings were carried out with variable energydynamic cone penetrometer. We used both Light Dynamic Penetrometer (DPL - Panda)and its Super Heavy version (DPSH - Grizzly), to evaluate the soil characteristics and tospecify the geometries of the various subsurface sedimentary layers. This paper presentsone of the ground site models based on DPL and DPSH tests along with Electrical ResistivityTomography (ERT) profiles. The resulting models will contribute to a better understanding ofmechanical characteristics of soils and their potential to liquefy

In an attempt to go beyond the conventional laboratory experiments widely reported in literature around the emerging technique ofsoil bio-cementation, this work addresses key challenges related to its large-scale application. Precisely, a state-of-the-art installation witha draining bottom boundary is introduced and a novel treatment strategy, based on ex-situ hydrolysis within a 1000 L bioreactor, isdescribed. Hydrolyzed solutions are injected in a tank filled with 0–4 mm sand, via a system of eight injection tubes to treat a total surfaceof 40 m2 across a depth of 2 m. A multilevel, spatial and temporal quality control system is used to monitor the injection processes acrossseveral cycles via chemical and hydraulic means. In total, 20.8 m3 of reactant solutions are supplied to the targeted zone, equal to onepore volume and over 120 chemical analyses are carried-out. Reaction efficiencies overall exceeded 80%, while by increasing the numberof treatment cycles, and thus calcification levels, a gradual increase in the recorded pressure at the injection inlet was captured, thatreached up to 75 kPa. Zones where the injection pressure increased the most are found to yield better resistance in the vicinity of thecorresponding injection tube. A dynamic penetrometer campaign reveals that increase in the tip resistance, is found to exceed 5 MPaand yields more homogenous response across the bottom 0.5 m of the tank, which is believed to reflect the effect of initial confinementon the deposition of calcite. For the zones with the highest cementation, correlated u’ values yield a 5
increase, while the oedometricmodulus is found to double. The results suggest that ex-situ bio-cementation, where hydrolysis occurs in bioreactors instead of inside thesoil mass, is capable of yielding similar precipitation efficiencies and mechanical improvement compared to traditional bio-cementation,where bacteria are injected directly into the soil. Finally, the monitoring of MICP at the scale of typical geotechnical works is discussedalong with the problematic of residual ammonium, which in this study is found to reach absorded quantities of 4 mol/L.

Fouling and deterioration of the ballast are a major problem in opera-tion of railway tracks. Its characterization is thus a fundamental task to optimize decision-making in maintenance or renewal programs. This study aims to char-acterize the fouled ballast using a dynamic penetrometer (PA.N.D.A) and geoen-doscope test1. The methodology presented consists in analyzing the resistance properties of each layer by means of dynamic cone resistance (qd) and then per-forming a geoendoscope test to obtain borehole images for a material character-ization. Statistical analysis of cone resistance and statistical image parameters (texture and colometry) shows their dependence on the degree of fouling as well as on its nature. As ballast fouling increases, the average cone resistance initially increases and then decreases. Images features also depend on the proportion of fouling but especially allow to distinguish different contents of fine pArticles in the fouling material. However, each of the measurements taken separately is not sufficient to determine a ballast fouling amount. In this way, a last study on data fusion has been carried out and shows an improvement in the quantification of the Fouling Index.

En raison de la difficulté de prélèvement d'échantillons non remaniés de sable, la possibilité d'évaluer directement sur site, à partir d'essais in situ, des paramètres de comportement contrainte-déformation pour les sables constitue un enjeu important en géotechnique. Récemment, un nouveau type d'essai au pénétromètre dynamique léger, à énergie variable, associé à une méthode d'analyse dynamique spécifique, a été développé. Le dispositif est entièrement instrumenté et le principe de base est d'analyser le phénomène de propagation d'ondes dans les tiges au cours de l'impact en vue d'obtenir, pour chaque impact, la courbe de chargement force-déplacement de la pointe et d'en tirer des paramètres élémentaires du sol. Dans ce contexte, un programme expérimental a été réalisé à l'aide de ce dispositif évalué en chambre d'étalonnage sur un sable de référence, le sable de Fontainebleau NE34. On a, en particulier, étudié l'influence de paramètres tels que l'état de densité du sable, l'état de contraintes appliqué au massif et l'état du sable (sec ou saturé) sur les résultats obtenus à l'aide de ce dispositif. Sur la base de l'analyse de ces résultats, on donne quelques pistes de réflexion concernant l'utilisation de ce dispositif pour l'évaluation du risque de liquéfaction des sables.

Leaching waste deposits are structures used for the storage of residues generated by hydrometallurgical processes forobtaining copper. Although the mechanical behavior of these types of deposits have historically remained adequate in seismicallyactive countries like Chile, it is necessary to evaluate – for closure and post-closure stages – long-term physical stability, potentialfailure mechanisms, slope stability, and seismically induced deformations. However, the physical and chemical characteristics ofsuch materials impedes geomechanical characterization via traditional in-situ and laboratory tests. Thus, this Article presents a costefficientmethodology to be implemented in evaluating long-term physical stability of leaching waste deposits. We identify the maincontributing failure mechanisms, estimate in-situ conditions, and present the geomechanical parameters for stored material mostsuitable for analysis.

Na geotecnia, as investigações de campo é uma etapa indispensável para o planejamento urbano, para avaliação e elaboração de projetos e, consequentemente, para execução das obras de Engenharia. Sempre buscando, quando possível, técnicas simples, com baixo custo, para a elaboração de bancos de dados, que são compostos por investigação para elaboração de cartas geotécnicas. As cartas geotécnicas destinadas ao planejamento auxiliam na iniciativa de políticas públicas de harmonização entre o processo de urbanização e meio ambiente.As tecnologias de processamento computacional de dados cartográficos tornaram possível manipular, gerenciar e finalmente analisar uma grande quantidade de dados referenciados espacialmente. O Ensaio de Simples Reconhecimento, ou Standard Penetration Test (SPT), é um ensaio muito utilizado no Brasil e no mundo pela simplicidade, robustez, baixo custo e alta experiência empírica acumulada. O ensaio realizado com o equipamento denominado penetrômetro dinâmico leve de energia variável (PANDA 2) fornece dados importantes do perfil geotécnico, por intermédio de aquisição automática em tempo real de uma forma simples e rápida.Foi proposto neste trabalho uma correlação entre os ensaios SPT e PANDA 2, sendo selecionada uma área que está inserida em uma região do Distrito Federal que está passando por um processo de planejamento de urbanização. A área selecionada para o estudo está localizada no Setor Habitacional Taquari Etapa II, inserida na Região Administrativa do Lago Norte.Nesta pesquisa foi proposto também um método de interpolação em ambiente SIG dos dados do PANDA 2 para diferentes profundidades até 4,5m e a partir da correlação dos dados de resistência a penetração SPT com o PANDA, foi realizada uma estimativa da distribuição espacial do valor do SPT para diferentes profundidades até 4,5m, a fim de colaborar com o processo de desenvolvimento urbano da região e fornecer dados para futuras pesquisas que sejam realizadas no setor.

En este trabajo se presenta la aplicación de modelosgeoestadísticos a 71 ensayos con penetrómetro dinámicopesado DPSH Grizzly® realizados durante los últimos7 años en una amplia zona del sector norte de la ciudadde Punta Arenas. Este sector, se caracteriza por tener unaextensa unidad, compuesta de arenas saturadas sueltaspotencialmente licuables, la que está acompañada deotras unidades de menor extensión compuesta por suelosorgánicos y arcillas blandas denominada localmente como“mazacote”. Los modelos geoestadísticos permitieronobtener una correlación espacial de los datos de resistenciapor punta del penetrómetro dinámico DPSH Grizzly®.Mediante estimaciones de interpolación geoestadísticoKriging, se identificaron las unidades geotécnicas queconforman el sector en estudio y también las zonas mássusceptibles al fenómeno de licuación. Se complementóel estudio con datos de sondajes SPT, cartas geológicas ygeomorfológicas y calibraciones al penetrómetro dinámicoDPSH Grizzly®, realizadas durante la ejecución y revisiónde los ensayos.

On a réalisé des essais pénétrométriques de chargement en pointe(dynamiques DCLT et statiques CLT) avec des sables de référence. En exploitant lescourbes DCLT, on estime les courbes CLT. Celles-ci présentent une bonne correspondanceavec les courbes expérimentales. Cette analyse permet de dissocier l’effet statique de l’effetdynamique et ouvre la voie à une meilleure interprétation de l’essai DCLT.