The infrastructure for hydrocarbon transportation has grown significantly to supply the needs of a greater number of settlements; however, due to problems in the supply networks, accidental spills or leaks can contaminate the underlying soils. This paper addresses soils contaminated with gasoline, and it analyzes the changes that occur in a tropical residual soil after contamination. Analysis was carried out by using specific laboratory tests to characterize the type of soil (Miniature Compacted Tropical Classification, Suction, Pinhole Test, Collapse Potential, X-ray Diffraction, Scanning Electron Microscopy, pH determination) and by performing traditional tests (natural humidity, specific gravity, granulometry, Atterberg limits, direct shear, etc.). These tests were conducted with samples in their natural state, as well as contaminated samples, in order to elucidate possible variations in the mechanical characteristics of the material.

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There are few studies on the processes involved in landslides in the soils of the Colombian coffee region in relation to the soil water content. In order to contribute to this knowledge, several experiments over a terrain model under simulated rainfall were conducted. Seven experiments on laboratory slope models, 1.8 m 2 base, 1.0 m height, and 32° slope, with soil bulk density and soil horizons arrangement similar to in situ conditions, were built. Samples of altered residual soil derived from granitic rocks were collected in the municipality of Ibagué-Colombia from the surface down to 1.6 m depth. In each laboratory model, eight suction tensiometers (0 to −85 kPa) were located, and measurement under simulated rainfall was done. The results indicated a relationship of mass movements with hydrological processes occurring in the slope, related to soil permeability, rainfall intensity and duration, and water table changes. The major portion of soil slope instability cases was related to a saturated condition of the slope toe.

Las zonas tropicales son regiones sometidas a ambientes cálidos, y sus suelos, en especial en aquellas áreas cubiertas de vegetación, pueden estar expuestos a eventos como los incendios. Las altas temperaturas que se pueden alcanzar en estos eventos causan variaciones en algunas de las propiedades geotécnicas de los suelos, influenciando el comportamiento del material, y pueden dar origen a procesos erosivos, que en muchos casos preceden a movimientos en masa. El siguiente artículo expone lo que ocurre en un suelo sometido a un proceso de ignición en el laboratorio, analizando las variaciones en algunas propiedades físicas (contenido de humedad, límites de Atterberg, gravedad específica y granulometría), químicas (pH y capacidad de intercambio catiónico), mineralógicas, estructurales y mecánicas (succión, desagregación y pinhole test); mostrando claramente que el material se torna más ácido con mayor relación de vacíos, menor capacidad de intercambio catiónico, menor cantidad de caolinita, plasticidad y succión, y variación en su textura, con un consecuente aumento en la erodabilidad.

Abstract. Some widely-graded soils may exhibit, under the influence of steady seepage flow, a behaviour in which grains of the finer fraction migrate through the interstices of the matrix formed by the coarser fraction. The migrating fines may accumulate at a downstream location within the soil. Alternatively, and where there is no capacity for retention at the downstream or exit boundary, the behaviour may lead to a washing out and consequent loss of the finer fraction. The phenomenon of erosion is termed internal instability, and the soils are considered internally unstable. Taking into consideration (i) the specimen reconstitution by method of compaction, (ii) the application of a vertical stress to the specimen, and (iii) the use of multi-stage seepage flow with head-control, to measure the origin of a conduit through the coarser fraction, some test devices were conducted by different authors to evaluate this phenomenon, the purpose of this paper is to present some considerations and key aspects about internal erosion in dams and filter compatibility with core material (specimen reconstitution, test procedure, consolidation, seepage flow, test program and its relevance to the reality). The main reason to present this investigation is due to the absence of any specified regulatory or standard test method. Given the importance of filter compatibility of the zoned earth core dam and filter materials, as well the grading stability of each zone in the presence of seepage flow, additional consideration will be given to performing Continuing Erosion Filter (CEF) tests on the core-filter interface, using the laboratory permeameter device.