Lateritic soils, characterized by complex mineralogy, a high degree of weathering, and a distinctive structure, are widely distributed in tropical regions. However, their use in pavement layers is often restricted due to conservative soil classification methods that may not fully represent their mechanical potential. This study evaluates the geotechnical behavior of a lateritic clay from a small town in São Paulo, referred to in this article as Purple Clay, with a focus on its permanent deformation (PD) and resilient modulus (RM). Repeated load triaxial tests, along with X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM), were conducted to assess the soil’s mechanical response and microscopic structure. The results indicated that the high concentration of iron oxides contributed to increased cohesion and mechanical strength. When compacted at intermediate Proctor energy, the Purple Clay exhibited RM values comparable to some granular materials reported in the literature, highlighting its potential for pavement applications. However, under higher stress levels, PD was up to 42% greater than that of reference materials, emphasizing the influence of loading conditions on its behavior.

Since the 70’s, when offshore oil exploitation advanced, submarine pipeline design has been the subject of many researcher studies. Pipeline free spans are common and frequently assessed. In spite of this, up to this day, there is no simple and specific formula to calculate the effective tension (S_eff), which takes into account the pipeline sagging in moderate or large span lengths. Therefore, engineers normally apply finite element analyses, even for preliminary evaluations. On the other hand, there are simple formulae to calculate other parameters such as the deflection, the moment and the natural frequency, which require previous knowledge of the S_eff value. In the present contribution, an approximate formula is proposed, in order to solve the beam differential equation for both pinned and fixed end conditions and make it possible to calculate the S_eff value using a straightforward and relatively simple equation, which takes into account the pipeline sagging. The values calculated using the proposed method were compared to numerical results obtained for many different cases, varying the span length and the effective tension. The analysis results showed that the proposed equation is highly accurate for practical conditions and, therefore, may become a useful tool for the assessment of the pipeline free spans.

This study investigates the influence of moisture on the mechanical behavior of fine soil mixtures from the São Luís region, applied as subballast layers in railway track structures. Two samples were analyzed: a non-lateritic sandy soil (NA’, AM03) and a lateritic clayey soil (LG’, AM09). The research included physical and chemical characterization tests, as well as repeated load triaxial tests to determine the resilient modulus and shakedown limits, complemented by numerical simulations using the SysTrain 2.0 software. The samples showed average resilient modulus values of 577 MPa and 638 MPa, respectively. Tests were conducted under optimum moisture content and under moisture 1% above the optimum, induced by capillary rise in compacted samples. The results indicated that under 1% above optimum moisture, the shakedown limits were reduced by up to 50% for AM03 and 25% for AM09, demonstrating greater stability for the lateritic soil. In addition, it was observed that as stress ratios increased, the shakedown limits for both moisture conditions tended to converge. Numerical simulations confirmed the adverse influence of increased moisture on the occurrence of shakedown in both samples. For AM03, the simulations revealed progressive failure under elevated moisture, indicating a more severe stress redistribution within the subballast layer. In contrast, AM09 remained within the shakedown regime under both conditions, although it exhibited higher values of $S_1/S_{1\max }$ under moisture above optimum, suggesting a greater tendency toward plastic creep. These findings highlight the critical importance of moisture control for the sustainable performance of railway substructures. This study contributes to understanding environmental vulnerability in transportation infrastructure and supports the development of more resilient and sustainable railway systems.

Several types of fishways are designed to allow the upstream passage of fish during the reproductive migration. Despite being the subject of many studies, improvements are still necessary to ensure an adequate flow for fish passage. This work aims to study the hydraulic parameters of the free-surface flow in the Igarapava HPP fishway, in Brazil, by comparing numerical results with available experimental data. Recent formulations for smoothed particle hydrodynamics were investigated in the numerical simulation using DualSPHysics. Open boundary conditions with buffer layers were applied to simulate inflow and outflow in the model. Three different model settings compared the effectiveness of the density diffusion term and the viscosity coefficient. Spurious oscillations were significantly reduced in the velocity field by using a combination of diffusion term and artificial viscosity coefficient that resulted in a smoothing effect near the walls and fewer oscillations in water level.

Dam break is one of the greatest hazards causing damages in urban and rural areas throughout the world. It can happen due to design and construction errors, heavy rainfall, earthquakes or glacier melting, among other reasons. Once the dam collapses, the resulting flow can become even worse due to obstacles, like houses, walls, bridges and trees, which can be impacted and transported along with the water. The prevention or reduction of the downstream effects of a dam break due to the complex and highly energized flow has been a challenge to researchers and engineers all over the world. The present study aimed to compare two free computer programs for numerical simulation of a flow with obstacles, based on available experimental data. These programs are based on the material point method (MPM) and smoothed particle hydrodynamics (SPH), respectively. The numerical results of the two programs were in good agreement with experimental data, although important differences in computing time were observed. Therefore, these methods seem to be potential tools for the prediction of dam-break flows.