Abstract The maximum shear modulus (G0) and the modulus degradation curve (G/G0 versus γ) are important information in the evaluation of the soil mechanical behavior, both for dynamic and static loads. Dynamic tests (resonant column and cyclic triaxial tests) are not routinely performed in geotechnical practice in Brazil, and the geotechnical literature on the dynamic behavior of unsaturated tropical soils is limited. This paper presents and discusses seismic dilatometer (SDMT), resonant column, and triaxial test with bender elements and internal instrumentation to determine G0 and the modulus degradation curve in an unsaturated tropical sandy soil profile. It was observed that G0 tends to increase non-linearly with soil suction and net stress (σ - ua). It was also observed that the in situ G0 values determined with the SDMT were higher than those from laboratory tests (bender elements and resonant column). The modulus degradation curves determined with resonant column were used to define the reference curve via SDMT for the studied site. Soil suction influence in shear modulus degradation curves determined with unsaturated triaxial compression tests with local instrumentation is also presented and discussed.

Abstract Maximum shear modulus (G0) has been used in various geotechnical jobs (e.g., seismic site assessment, machine vibration and pile driven). Laboratory and in situ determination of G0 is not a current practice in Brazil. G0 can be estimated from empirical correlations based on in situ tests like Standard Penetration Test (SPT) and Cone Penetration Test (CPT) in the preliminary design phase. Several empirical correlations to estimate G0 from SPT N value have been developed and are available in the literature. However, most of these correlations were established based on experience with well-behaved soils formed in temperate and glacial zones, which may not always be used for tropical soils. This paper assessed and discussed the applicability of some correlations for G0 estimative from SPT data in lateritic and saprolitic soils. The classical correlations for sedimentary soils underestimated G0 of tropical soils. After updating the database, the tropical soils correlations reasonably estimated G0 for the lateritic ones, which was not the case for the saprolitic soils. It was observed that differentiating the soils only as lateritic or saprolitic was not adequate for a good G0 estimate for the saprolitic sandy soils. It was found that only the lateritic soils correlation can be used with caution as a preliminary attempt to estimate G0 from SPT N value in soils with similar characteristics to the ones presented in this paper.

Abstract The mechanical behavior of municipal solid waste (MSW) is a critical issue in environmental geotechnics, given the pollution and public health risks associated with slope failures. In Brazil, waste composition is expected to change due to the hierarchy of sustainable practices established by the National Solid Waste Policy, which aims to improve the recovery of organic and recyclable materials. Not much progress has been made since the implementation of this law; thus, its effects on the design and operation of landfills are not fully clear. This study presents and discusses compaction and shear strength parameters of dry MSW after mechanical sorting of medium and large recyclable items and shredding. The maximum dry unit weight for the standard Proctor compaction test ranged from 6.6 to 10.0 kN/m3 and the optimum moisture content ranged from 20% to 42%. Stress-displacement curves of direct shear tests showed strain hardening and shear strength parameters of Mohr-Coulomb envelopes were displacement-dependent. The friction angle ranged from 3.2° to 42.9° and the cohesion intercept ranged from 1.3 to 31.3 kPa, at a displacement of 9 mm (15% of the specimen length). These results are in line with the literature, since a high content of waste materials that proved to affect geotechnical properties, such as plastic, paper, cardboard, textile, and glass, remained after pre-treatment.

Abstract The slope stability is an important topic because it presents risks of socio-economic losses caused by eventual ruptures. It is necessary to identify the site profile, as well as obtaining soil strength parameters for the slope stability analysis. This paper presents and discusses the use of the Flat Dilatometer Test (DMT) in the geotechnical site characterization for slope stability analysis in an unsaturated tropical soil site. Six DMTs were performed to define the stratigraphical profile and estimate geotechnical parameters. Shear strength parameters were determined in the laboratory using saturated and unsaturated triaxial compression as well as soil water retention curves (SWRC) to support DMT data interpretation. A commercial software was used to perform the slope stability analysis a cut slope with 6.6 m height and a gradient around 55° to illustrate the application of DMT and triaxial test data. The DMT allowed the representative site profile to be identified, as well as estimating the design parameters that compared well to those interpreted from unsaturated triaxial test data for the in-situ soil suction. The DMT can be used as logging test in the preliminary characterization of studied site specially to define the stratigraphical profile, site variability, select the regions to collect disturbed and undisturbed soil samples and as the first attempt to estimate the geotechnical design parameters via correlations. It is important to emphasize that laboratory tests on undisturbed soil samples are essential in the slope stability analysis of unsaturated tropical soil profiles.

Abstract Geophysical methods are potent tools for geotechnical site characterization in a non-destructive way. They improve the extrapolation of punctual data from direct survey methods, allowing a fast and cost-effective evaluation of large areas. Ground Penetrating Radar (GPR) and DC electrical resistivity (ER) are the most requested methods for geotechnical and geoenvironmental applications. Their use, however, is usually uncoupled, with no sharing of information from one method to another to improve data interpretation. This case study illustrates the development of protocols and scripts in R© programming language for ER and GPR data analysis with Standard Penetration Tests (SPT) data to produce more accurate information on subsurface conditions concerning lithology, water content, and groundwater table (GWT) position. The SPT data were used to associate resistivity ranges with different soil lithologies and GPR pulse velocities for estimating the soil water content. Estimated water content values aided in interpreting ER data and locating the groundwater table. The contacts between layers in the radargrams allowed the refinement of the ER model, rendering 3D volumes for each soil layer in situ. nondestructive non destructive way costeffective cost effective areas (GPR (ER applications use however uncoupled interpretation R (SPT lithology GWT (GWT position model D situ

Abstract In 2019, a massive oil spill impacted coastal ecosystems in eleven Brazilian states; these ecosystems were diverse with regard to their different geological settings (sandy beaches, rocky coasts, estuaries, tidal flats, mangroves, and reef systems) being impacted. Here, we present a temporal analysis on the occurrence of remaining contaminants on three beaches (Paiva, Itapuama, and Enseada) of the Cabo de Santo Agostinho City, Pernambuco State. The approach focuses on the systematic mapping of residues, collection of sediment samples, photographic documentation, and qualitative microscopic analysis. Grain size, calcium carbonate, and total organic matter content analyses provided a faciological and energetic characterization of the environment. The objective was to verify the relationship between the remaining contaminants and the geological setting. The results showed intense weathering of the remaining oil residues due to the high energy environment. We found tar balls reworked by seasonal erosion on the three beaches and no tar residues in shallow subsurface sediments. A large quantity of tar residues remains on rock surfaces in Itapuama Beach, which bears the higher permanence of contamination because it is less affected by weathering and beach erosion. This investigation allowed for an impact assessment of the geological-morphological characteristics of the beaches.

Abstract The seasonal variability of geotechnical parameters in the unsaturated zone is typically neglected in the design of geotechnical works. In most of the geotechnical projects the parameters are determined only for the saturated condition. Although it is known that this condition is the most critical to soil strength and deformability, this conservative approach may neglect a possible important contribution of the unsaturated condition, resulting in an increase in the cost of the geotechnical solution. This paper presents and discusses the site characterization of the active zone of an unsaturated sandy soil profile under different suction conditions. Laboratory tests with controlled suction (retention curves, triaxial compression with bender elements and oedometer tests) were carried out on undisturbed samples collected from 1.0 to 5.0 m depth. The results show that strength and deformability parameters are strongly affected by soil suction and are less influenced by confinement stress up to 5.0 m depth. All the investigated subsoil profile shows a collapsible behavior, more pronounced closer to the ground surface and under the effect of higher suction values. The findings highlight the importance of incorporating the suction influence in the site investigation, parameter determination, and geotechnical design for more economical, reliable, and environmentally sustainable solutions.

Resumen Este artículo presenta la caracterización geotécnica de un perfil de suelo tropical no saturado de un campo experimental localizado en la ciudad de Bauru, São Paulo, Brasil. Fueron ejecutadas varias campañas in-situ, que incluyen ensayos geofísicos (cross-hole, down-hole y up-hole con ensayos SPT) y ensayos mecánicos (SPT, CPT e SDMT). Según el sistema de clasificación MCT, los primeros 13 m del sitio de estudio corresponden a un colúvio de matriz arenosa con comportamiento laterítico (LA'), seguido por un suelo residual de comportamiento no laterítico (NA'). La relación obtenida entre los parámetros sísmicos ( Go ) y mecánicos ( qn, N60, ED, KD e MDMT ) permitió identificar la presencia de microestructuras y confirmar el comportamiento específico de este material. Los ensayos de CPT y SDMT fueron eficientes para definir detalladamente el perfil estratigráfico; no obstante, la estimativa de los parámetros geotécnicos no puede ser realizada basada únicamente en correlaciones convencionales definidas para suelos sedimentares.

Abstract This paper compiles site characterization data of an unsaturated tropical soil profile in an experimental research site in Bauru, São Paulo State, Brazil. Several in situ campaigns comprised geophysical borehole tests (cross-hole, down-hole and up-hole together with the SPT), as well as mechanical tests (SPT, CPT and SDMT) have been performed. According to the MCT Classification System for tropical soils, the first 13 m depth is a colluvium with lateritic soil behavior (LA’) over the residual soil with non-lateritic behavior (NA’). The ratio between seismic ( Go ) and mechanical ( qn, N60, ED, KD and MDMT ) parameters was useful to identify the presence of microstructure and to confirm unusual soil behavior for this tropical soil site. CPT and SDMT were efficient for detailed stratigraphic logging, however, the estimative of geotechnical parameters cannot be solely been done base on just conventional correlations defined for sedimentary soil.

RESUMO Este artigo apresenta o monitoramento ambiental das águas subterrâneas do entorno do aterro de resíduos sólidos urbanos (RSU) de Bauru, São Paulo, Brasil. Paralelamente às diversas pesquisas realizadas na área durante o período de janeiro de 2003 a abril de 2008, foram construídos 14 poços de monitoramento em diferentes fases da investigação geoambiental, seguindo as normas vigentes na época e as necessidades observadas durante a interpretação dos resultados desta investigação, para confirmação da contaminação da área. As amostras foram coletadas com bailer , após o período de chuvas e de estiagem de cada ano. São apresentados os resultados obtidos ao longo do tempo para os seguintes parâmetros: nível d'água, pH, condutividade elétrica (CE), Ca2+, Cl, Fe total, DQO, NH4 +, Zn2+, Na+, K+, além da relação demanda biológica de oxigênio/demanda química de oxigênio (DBO/DQO). Os resultados do longo período de monitoramento permitiram a análise de cada parâmetro em função do que ocorria superficialmente ao aterro, assim como com características naturais do aquífero. Conclui-se que a pluma de contaminação varia conforme o ponto de disposição e as características dos resíduos depositados, cuja recuperação e atenuação deverão ocorrer com o encerramento das atividades do aterro.

ABSTRACT This paper presents the environmental monitoring of the groundwater surrounding the municipal solid waste disposal site from Bauru, São Paulo, Brazil. In parallel with the several surveys carried out at this site, between January 2003 and April 2008, fourteen monitoring wells were installed at different periods of the geoenvironmental site investigation, following the Brazilian standards valid at that time and the demands observed with the interpretation of the site investigation data, to confirm the local contamination. The samples were collected using bailer, after rains and drought periods each year. The results obtained over time are presented, for the following parameters: groundwater table, pH, electrical conductivity, Ca2+, Cl, total Fe, DQO, NH4 +, Zn2+, Na+, K+, and the ratio BOD/COD. The results of the long period of monitoring allowed the analysis of each parameter compared with what was happening superficially on the landfill, as well as natural characteristics of the aquifer. It is concluded that the contamination plume varies according to the layout and characteristics of the disposed waste, which recovery and mitigation should occur with the closure of the landfill.

A geofísica tem mostrado eficácia em identificar áreas contaminadas pela disposição de resíduos sólidos urbanos, contribuindo para tornar mais efetivos os programas de sondagem voltados à coleta de amostras e instalação de sistemas de monitoramento. Dentro desse contexto, este trabalho teve como finalidade avaliar as potencialidades da integração dos métodos geofísicos (eletrorresistividade, polarização induzida e potencial espontâneo) na caracterização geoambiental da área do aterro sanitário da cidade de Bauru-SP. O método do potencial espontâneo permitiu detectar o sentido do fluxo subterrâneo. Os métodos da eletrorresistividade e polarização induzida permitiram identificar anomalias dentro da zona saturada, que caracterizaram a presença da contaminação gerada pela migração do percolado proveniente da disposição dos resíduos sólidos. A contaminação é confirmada por investigação direta (análise química da água coletada nos poços de monitoramento). Os métodos geofísicos utilizados forneceram um grande número de informações sobre as diversas características relacionadas à interação entre a área de disposição de resíduos sólidos urbanos e o meio físico.

Geophysics has shown effectiveness in identify areas contaminated by urban solid wastes, contributing to become more effective sounding programs directed to collect of samples and installation of monitoring systems. In this context, this work had as purpose evaluating the potentialities of the integration of geophysical methods (resistivity, induced polarization and self-potential) in the environmental characterization of the area of the sanitary landfill of the city of Bauru-SP. The self-potential method allowed to detect the direction of the underground flow. The resistivity and induced polarization methods allowed to identify anomalies inside of the saturated zone, that characterize the presence of contamination generated for the migration of the percolated proceeding of the disposal of solid waste. This contamination is confirmed by direct investigation (chemical analysis of the water collected in the monitoring wells). The geophysical methods used had supplied a great number of information about the several characteristics related to interaction between waste disposal area and environment.

Neste estudo avaliou-se o transporte de líquidos e a atenuação da carga orgânica do chorume de aterro sanitário em um solo arenoso fino, compactado com diferentes graus de compactação. Para tanto foram construídas colunas de 1 m do solo compactado com 75 (natural), 80, 85, 90 e 95% do Proctor Normal, que foram alimentadas com água e com chorume, sob condições não saturadas. Foram verificadas reduções sensíveis na permeabilidade do chorume e na remoção de DQO para as colunas submetidas a graus de compactação igual ou superior a 85%. Os resultados desta pesquisa mostram o grande potencial de uso deste solo compactado, em bases de aterros sanitários de pequeno porte, para a retenção da carga orgânica de chorume.

Water and leachate flow and COD attenuation through a fine sandy soil at different compaction degree were assessed, based on column tests results. Each column was 1.0 m deep and 0.097 m in diameter, and the soil was compacted with 75 (natural), 80, 85, 90 and 95% of Standard Proctor Test, to receive water or sanitary landfill leachate under unsaturated conditions. During the experiment, COD removal and leachate permeability reduction were very significant for columns with 85% or higher compaction levels. The results show the high potential of this practice to install simple system in small sanitary landfills, for leachate organic loading retention.