A series of bender element tests and drained and undrained monotonic triaxial compression and extension tests were performed on air-pluviated samples of Hostun sand. Samples were prepared to different initial void ratios, consolidated under various isotropic and anisotropic stress states, and sheared using different stress paths and a wide range of deformations to characterize the sand’s stress-strain response. The results suggest that the sand’s small-strain behavior essentially depends on the current void ratio and mean effective stress. Within the medium to large strain range, a state-parameter approach in conjunction with the critical-state framework can successfully predict the distinctive states of the sand’s monotonic response, namely the phase-transformation, peak-stress-ratio, and critical states. Furthermore, the data are used to examine a stress-dilatancy relationship often incorporated in constitutive models. The characterization presented herein aims at assisting the efficient calibration of numerical models and provides insight into this sand’s behavior, thus supporting the interpretation of results of physical modeling involving this sand. This paper highlights the importance of characterizing sand’s behavior over the full strain range and shows that accurate predictions of the critical state and small-strain stiffness are crucial to assess other aspects of the sand’s behavior.

This paper compares the behavior of an embankment with nonsymmetric geometry built on soft soil with that predicted numerically using four elastoplastic soil models. Two of these models are based on isotropic conditions (Modified Cam-Clay on its own or in association with Von Mises) and two other are derived from anisotropic conditions (Melanie on its own or conjugated with Mohr Coulomb). The performance of the models, whose parameters are derived from experimental data, is checked against triaxial tests results. For the embankment, the measured and computed displacements and excess pore pressure are compared, with the isotropic models performing best. The maximum horizontal displacements versus settlements, the change in excess pore pressure versus vertical stress, the extent of the yield domain and the contours of the effective vertical and horizontal stress increments are also examined. The numerical results are explained based on the characteristics of the numerical models, namely the size and shape o...

The mining industry produces large amounts of tailings which are disposed of in deposits, which neglects their potential value and represents important economic, social and environmental risks. Consequently, implementing circular economy principles using these unconventional geomaterials may decrease the wide-ranging impacts of raw material extraction. This paper presents an experimental characterization of iron ore tailings, which are the most abundant type of mining waste. The characterization includes various aspects of behavior that are relevant to different types of use as a building material, including physical and identification properties, compaction behavior and stress–strain properties under undrained monotonic and cyclic triaxial loading. The tailings tested can be described as low-plasticity silty sand materials with an average solids density of 4.7, a maximum dry unit weight close to 3 g/cm³ and a higher angle of friction and liquefaction resistance than common granular materials. The experimental results highlight the particular features of the behavior of iron ore tailings and emphasize the potentially promising combination of high shear resistance and high density that favors particular geotechnical applications. Overall, the conclusions provide the basis for promoting the use of mining wastes in the construction of sustainable geotechnical works and underpin the advanced analysis of tailings storage facilities’ safety founded on an open-minded geotechnical approach.

The combined effects of wildfires and storms strongly induce slopes stability phenomena, thus requiring mitigation measures to manage long-lasting wildfire-induced risks. In Portugal, thousands of increasingly destructive wildfires occur during the hottest months. In the last two decades, almost 3,000,000 ha of forest, bush and agricultural land burned in Portugal, 20% of which caused by massive wildfires that occurred in 2017. Portuguese central mountain range was one of the most affected areas, namely the study area of Serra do Açor and Serra da Estrela, where extreme rainfall events in 2018 and 2019 caused extensive slope instability phenomena that created a unique opportunity for assessing long-term field performance of treated and untreated burnt areas. The registered phenomena as well as the treatment solutions applied to mitigate instability effects on slopes were studied in two sites. Over 3 years, several field research trips were carried out to scientifically assess the situation over time. By comparing areas with distinct response to the extreme rainfall events and based on the data collected, namely prior to 2017, it was been possible to link the registered instability events and the October 2017 wildfires and qualitatively evaluate the effectiveness of the adopted mitigation solutions. This study not only confirms that the study area is prone to slope instability wildfire-related phenomena, with a 13-year return period between similar events in the study area, but also validates the use of protective barriers as a mitigation measure, contrary to previous studies carried out in other countries.

The selection of the macrolocation of new high-speed rail (HSR) systems during the planning stage affects the associated infrastructure costs. The process is influenced by the complex interaction between the HSR alignment, the technical solutions, and the characteristics of the deployment site, subject to layout restrictions. Decision support systems for the optimization of the HSR alignment are developed for addressing the requirements of large and complex real projects. The formulation includes costs, geometric constraints, connection requirements, and consideration of natural barriers such as protected land use and bodies of water, ubiquitous in real projects. The simulated annealing algorithm is implemented to address challenges of real problems and solve the optimization model. The approach is applied to a Portuguese HSR case. The solution obtained optimizes its alignment by minimizing the construction costs, consistent with existing projects worldwide, and complying with location, geometry, ...