The presence of unsaturated flow in tropical lateritic soils of unknown hydromechanical behavior may lead to severe geotechnical problems. It is known that soil-water characteristic curves (SWCC) are a valuable tool to define this behavior and facilitate the suction estimation, acting on tests performed with no control of such parameter. This article aimed to determine and model the SWCC for 3 unprecedented tropical soils, in the undisturbed and the compacted conditions, from the Paraná state, located in the south of Brazil. The soils studied are one clay and two sands, all lateritic. The pressure plate and the filter paper methods were used to determine the SWCC. The samples were carved and submitted to the drying paths. Furthermore, Mercury Intrusion Porosimetry (MIP) tests were performed in samples of the studied soils in order to obtain the pore size distribution (PSD), contributing to the bimodal definition of curves and the prediction of SWCC main parameters. Both techniques (pressure plate and filter paper) were combined and the SWCC was adjusted by Gitirana & Fredlund model, which efficiently represents the shape of the traditional curves for tropical soils. Furthermore, the SWCCs were predicted by PSD and obtained satisfactory numerical fits. All SWCC presented air entry values in the macropores that are characteristic of soils as the lateritic, given that its structure was considered a key factor in the shape of the curves.

Superficial erosion is one of the main soil degradation agents and erosion rates estimations for different edaphicclimate conditions for the conventional models, as USLE and RUSLE, are expensive and time-consuming. The use of cesium-137 antrophogenic radionuclide is a new methodology that has been much studied and its application in the erosion soil evaluation has grown in countries as USA, UK, Australia and others. A brief narration of this methodology is being presented, as the development of the equations utilized for the erosion rates quantification through the cesium-137 measurements. Two watersheds studied in Brazil have shown that the cesium-137 methodology was practicable and coherent with the survey in field for applications in erosion studies.

The large amounts of construction waste (CW) generated yearly and its high landfilled proportion worldwide motivate the search for sustainable solutions. Thus, the effect of sandy soil partial replacement for construction waste in cemented mixtures was assessed in the present work in terms of mechanical behavior and microstructure. Distinct cement contents, compaction efforts, and curing periods were evaluated from soil-waste proportion of S75W25, S50W50, and S25W75. Tests of unconfined compression strength (UCS), indirect tensile strength (ITS), ultrasonic pulse velocity, water absorption, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) were conducted. The presence and increase in the amounts of cement and construction waste increase the optimum moisture content of the mixture. In contrast, only the CW content significantly affects maximum dry density. Both S75W25 and S50W50 mixtures resulted in similar UCS and ITS values, which was proven to be statistically equal by analysis of variance (ANOVA) at a 0.05 significance level, favoring CW replacing soil up to 50%. MIP and SEM results explained the sharp mechanical behavior transition obtained in 75% of CW. Cementation reactions resulted in macropores peak reduction and/or peak area translation to the left of the horizontal axis of the PSD curve, while its translation to the right indicates the cement mainly acting as filler, which was supported by SEM tests.