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The occurrence of lateritic soils with clayey texture, unsaturated, and with high porosity is common in Brazil. When subjected to an increase in moisture (loss of suction) in the more superficial layers, such soils end up altering their stress–strain behaviors, which are complex, culminating in countless geotechnical uncertainties. A phenomenon referred to as collapse is attributed to materials subjected to variation in saturation that entail significant differential settlements. Considering this situation, following the implementation of the Geotechnical Engineering Experimental Field located in the state of Rio Grande do Sul, Brazil, a broad study involving laboratory tests (granulometry, x-ray diffraction, water retention curve, confined compression, direct shear (natural and inundated condition), and consolidated drained triaxial compression tests) and field tests (SPT and static pile load tests) was carried out in the natural moisture and inundated conditions to assess the conditions of saturation and loss of suction in such materials. The results indicated that the shear strength of the soil was linked to the suction, having an 81.34% decrease in the cohesive intercept, and practically maintaining the soil friction angle. Confined compression tests with inundation indicated that the soil presented itself as potentially collapsible. The results obtained from the conducted pile load tests, revealing a substantial decline in carrying capacity ranging from 29 to 43% attributed to saturation of unsaturated soils, emphasize the paramount significance of this scientific article in comprehending the potential hazards associated with diminished bearing capacity and the subsequent emergence of structural pathologies or, in extreme cases, structural collapse. [ABSTRACT FROM AUTHOR]

This study aims to determine and to model the relationship of matric suction versus water content, known as soil-water characteristic curve (SWCC), for a tropical soil profile at the southeastern Brazil. This soil profile consists of a colluvial, lateritic silty clay, with thickness of about 6.5 m. The filter paper and pressure plate techniques were used to determine the SWCC. Specimens were trimmed from the undisturbed soil samples collected along soil profile depth and submitted to drying paths. Impregnated thin-layer plates and a petrographic microscope were used to examine the structure and mineralogical composition of the soil samples. Mercury intrusion porosimetry tests were performed on some soil samples to obtain the frequency histogram of the pores. SWCC with bimodal pore-size distribution were obtained by the filter paper technique and SWCC with unimodal pore-size distribution were obtained by the pressure plate technique. The SWCC showed values of air-entry ranging from 1 to 3 kPa, depending on the technique used, resembling soils with macroporosity, as the lateritic soils. Combining both techniques, the SWCC could be fitted by a model that takes into consideration soils with macro and microporosity. [ABSTRACT FROM AUTHOR]

Pyritic coal wastes produced by a coal beneficiation plant in the State of Santa Catarina in southern Brazil are acid generating. In this paper, we report the results from the first phase of a study evaluating the performance of dry covers for minimizing generation of acid mine drainage and its release to the environment. The first phase includes our investigation of locally available materials for dry covers. Numerical modeling led to four configurations being selected for testing: a dry cover using a double capillary barrier with bottom ash, a dry cover with a single layer of clay, a dry cover with mixed waste, and waste with no cover. Modeling also showed that the best position for the lysimeter was at the bottom of the excavation, where it would not interfere with the water flux in the waste. A subsequent paper will describe the construction of the experimental unit and the results of the geotechnical and geochemical studies. [ABSTRACT FROM AUTHOR]

This study was carried out in the Córrego do Vaçununga basin constituted of eolic sandstones of Botucatu Formation and residual unconsolidated materials (>90%), considered the most important unconfined aquifer in Brazil, in the city of Luiz Antonio, State of São Paulo, Brazil. Laboratory and in situ tests were performed to characterize the unconsolidated materials in terms of basic physical properties, potential infiltration rate, suction and hydraulic conductivity. The results for infiltration and overland flow depths were obtained according to Morel-Seytoux and Khanji (Water Resour Res 10(4):795–800, ) and Chu (Water Resour Res 14(3):461–466, ) adaptation of the Green and Ampt [J Agr Sci 4(Part 1):1–24, ] model for steady and transient rainfalls, respectively. Rainfall data were collected from January of 2000 to December of 2002, and 12 scenarios were defined considering the intensity and durations. Rather than high homogeneity in terms of the texture of unconsolidated materials, the infiltration and overland flow ratio depends on the type of land use and associated management practices. The results showed that rainfall with high intensity and short duration do not produce high overland flow ratio as we have observed for transient scenarios with long duration and low intensities. [ABSTRACT FROM AUTHOR]