Resumo em Inglês:

Abstract This article, a written contribution of the 10th James K. Mitchell, delivered in Bologna on June, 10, 2022, describes the experimental characterisation of Brumadinho B1 tailings dam, that allowed to study analytically a unique case history, of a massive earthwork which suddenly failed on January 25th of 2019 in Minas Gerais (Brazil). This detailed characterisation comprised an advanced experimental programme using reconstituted and undisturbed samples recoiled in three sampling campaigns in the remaining post-morten dam/reservoir tailings, where the failure mechanism developed. The results that embrace evaluations of the physical, hydraulic, and mechanical properties, allowed to define the geotechnical parameters necessary for the referred analyses. This cannot be completed without knowing how to deal with a heterogeneous distribution of types of tailings generated from distinct iron rock masses in the mine, which was pursued with re-interpretation of in situ tests, some recent with high quality data, clustering in zones that could be discretized by overall types of soils with proper index behaviour and state conditions. The necessary parameters for constitutive models based on Critical State Soil Mechanics with Instability Locus that could be used in stability numerical simulations, will be discussed – in their conditions - that can define a reliable back calculation of the failure.

Resumo em Inglês:

Abstract This paper will discuss the various challenges and issues associated with the design of foundations for tall buildings. A three-stage approach to design will be described, involving a preliminary stage, a detailed stage, and a final stage. In each stage, the parameters and the design analysis involved should be consistent. The various risk factors in the design will be outlined, together with the measures that can be taken to reduce these risks. The critical importance of the geotechnical characterization of the site will be emphasized and the assessment of the key parameters will be discussed. Two examples of the application of the design process to tall buildings, one in Dubai and the other in South Korea, will be presented. Finally, another issue that may be of importance in congested urban environments, multiple building interaction, will be mentioned.

Resumo em Inglês:

Abstract To ensure structural safety, understanding the behavior of foundations on collapsible soils under moisture variation is crucial. This study evaluates the performance of isolated footings installed in collapsible soil from Uberlândia (MG) under two scenarios: directly flooded without preloading, and preloaded before flooding. Both footings were subjected to slow static load tests and analyzed through three-dimensional numerical modeling using RS3 software. The results demonstrated a significant reduction in bearing capacity when flooding occurred prior to loading (up to 64%), compared to a 24% reduction when preloading was applied before inundation. The stress–settlement curves further revealed that preloading led to stiffer soil response and higher bearing capacity, with a 53% increase at 25 mm settlement compared to the non-preloaded case. These findings highlight the effectiveness of preloading in improving the performance of shallow foundations on collapsible soils under saturated conditions.

Resumo em Inglês:

Abstract This article presents the results of innovative laboratory tests conducted on different types of cubic gabion boxes, each with approximate edge length of 1 m. The tests evaluated both confined and unconfined boxes subjected to compression stresses. In addition to the confinement factor, the experimental variables included the type of mesh, the presence of tie rods, and the apparent density. The primary goal was to conduct a comparative analysis of the deformability of the boxes by measuring their horizontal and vertical displacements under controlled conditions of uniformly distributed vertical loading. The results indicate that double-twist hexagonal mesh gabions, which are traditionally used in geotechnical applications in Brazil, can support less load. However, due to their woven mesh configuration and geometric characteristics, they exhibit greater flexibility, allowing for more significant deformations. In contrast, welded mesh gabions, which are square or rectangular and constructed with higher-strength, larger-gauge carbon steel wires, are capable of supporting higher loads. Comparative analyses of tests conducted with and without confinement revealed that, when the boxes are filled carefully, the tests without confinement can yield very satisfactory results in a simpler way.

Resumo em Inglês:

Abstract The disposal of water treatment sludge (WTS) remains a major environmental challenge, especially in developing countries. This study evaluates the incorporation of WTS into silty clayey soils, with and without nonwoven geotextile reinforcement, to assess the mechanical and hydraulic behavior of mixtures for sanitary landfill applications. Laboratory tests—including compaction, confined compression, hydraulic conductivity, and direct shear—were performed on mixtures with 0–10% WTS and pure sludge. Results showed that increasing WTS content raised void ratios, reduced maximum dry unit weights, and lowered hydraulic conductivity, suggesting potential as a low-permeability barrier. However, higher WTS contents also increased compressibility and reduced shear strength, which may compromise stability. The 7.5% mixture maintained shear strength comparable to natural soil, representing an optimal balance between performance and sustainability. Geotextile reinforcement further improved shear strength in all mixtures, particularly under higher confining stresses, expanding applicability in engineered barriers. Overall, the findings confirm the viability of reusing untreated WTS as a partial soil substitute in landfill construction, contributing to resource conservation and sustainable waste management.

Resumo em Inglês:

Abstract This study proposes a methodology to evaluate correlations between credible failure modes and risk controls for Tailings Storage Facilities (TSFs), considering its characteristics and similarity. Additionally, this research proposes a decision tree framework developed to serve as a reference for analyzing credible failure modes during the risk assessment of a TSF. A dataset of 66 collapsed TSFs with known failure modes was analyzed. Variables included processed ore type, construction material and method, height, volume, seismic risk, and climate. The dataset was assessed for representativeness and to identify potential correlations for predicting structure behavior related to failure modes. Results showed that 21% of dams failing due to seismic liquefaction were in very high seismic risk zones, with 18% located in temperate climates. Upstream construction methods exhibited significant associations with static liquefaction (21%), seismic liquefaction (19%), and overtopping (12%). Regarding dam material, 15% of failures due to seismic liquefaction involved specific materials. Height and volume had minimal influence on failure modes within the analyzed dataset. These findings demonstrate the influence of structural characteristics on failure modes, enabling the correlation of applicable risk controls with TSF management and governance.

Resumo em Inglês:

Abstract This study presents a detailed characterization of the inherent variability of a silty gold tailings deposit on the basis of piezocone penetration test (CPTu) data. The database originates from a comprehensive site investigation campaign and was processed via a layer separation algorithm to identify strata and determine relevant statistical parameters. Profiles were classified considering granular (drained), intermediate (partially drained), and fine (undrained) material behavior, allowing for behavior-specific probabilistic analysis of cone resistance (qc), sleeve friction (fs), and pore pressure (u2). The results revealed greater measurement variability for qc, fs, and u2 in coarse-grained materials, whereas the strength parameters—particularly the undrained shear strength (Su)—exhibit greater variability in fine-grained materials. The classification approach also enabled a consistent estimation of the scale of fluctuation, an essential parameter for spatial variability modeling. A complementary numerical analysis illustrated the influence of inherent variability on the normalized cone resistance (qc/qcUD) under different drainage conditions. Greater dispersion occurred at lower velocities, which is characteristic of drained behavior. The alignment between the theoretical bounds and field data supports the robustness of the methodology, providing a valuable framework for reliability-based geotechnical design.

Resumo em Inglês:

Abstract Torpedo piles are widely used as anchoring systems in offshore structures due to their simplicity, low cost, and ease of installation. However, their limited vertical holding capacity requires operation under inclined loads to achieve the desired resistance, resulting in undesirable congestion of anchor lines in the production zone. This study investigates thermal consolidation as a strategy to enhance the vertical capacity of torpedo piles by using the pile itself as a heat source. Heating fine-grained soils, such as marine clays, generates a temporary increase in pore pressure which, upon dissipation, induces thermal consolidation around the pile and improves its holding capacity. Geotechnical centrifuge tests were performed to assess the influence of thermal gradients on soil mechanical behavior and soil–torpedo interaction. The results indicate a significant increase in undrained shear strength, as confirmed by T-bar tests, demonstrating the potential of thermal treatment to improve anchoring performance.

Resumo em Inglês:

Abstract Geobags have been applied in many coastal protection solutions giving them effective performance against cyclic hydrodynamic loading. However, polymer materials, such as the geotextiles used for geobags production, are susceptible to environmental degradation which is critical for engineering applications. This study aims to investigate the durability of woven polypropylene geotextiles under coastal environmental conditions, considering different exposure surface characteristics, such as varied slope surfaces, type of application surface, and surface color. Exposure panels were constructed, and geotextiles samples were exposed to the coast environment of Natal (Brazil) for period reached 492 days, during which specimens were collected, and geotextile tensile properties have been obtained as a reference of material degradation. Results indicated a strength depletion of 35% by the end of the exposure period. No significant influence of surface inclination on degradation was observed, while surface color emerged as a potentially influential factor. The findings of this study are essential for informing the design and implementation of mitigation strategies in coastal engineering works involving geosynthetics.

Resumo em Inglês:

Abstract In geotechnical engineering, soil strength parameters are fundamental to design. Field and laboratory tests are essential, yet they often involve practical and financial constraints. Traditional approaches based on empirical or theoretical relationships may not adequately capture the complexity of soil behavior. This study investigates the use of artificial intelligence as an alternative approach to address these limitations. A predictive model was developed to represent the stress–strain response obtained from direct shear tests on sandy materials. Data compiled and digitized from multiple published sources were used to build an experimental dataset for training three machine learning (ML) algorithms: Support Vector Regression (SVR), Random Forest (RF), and Feedforward Neural Network (FNN). The models were evaluated using performance metrics and validation test curves. Among them, RF produced the most consistent performance. SVR and FNN also showed satisfactory results, although to a lesser extent. These findings indicate that ML techniques, particularly RF, can provide useful support for geotechnical engineers and researchers in predicting the behavior of sands, even when working with a relatively limited dataset.

Resumo em Inglês:

Abstract This study investigated the mechanical behavior of tropical soils, specifically lateritic clays (LG') compacted under intermediate energy, with a focus on the analysis on resilient modulus (RM) and permanent deformation (PD). A database was compiled including 20 Brazilian soils, comprising physical properties (maximum dry density, optimum moisture content, particle size distribution, and MCT classification indices) and mechanical properties data from repeated load triaxial tests. RM and PD regression parameters were evaluated for different stress states, adhering to Brazilian regulations. RM results showed high variability (mean: 351 MPa; CV: 42%), demonstrating a strong influence of deviatoric stress, which significantly reduced the elastic response with increasing stress levels. PD followed a log-normal distribution (mean: 0.635%; CV: 141%), with greater deformation correlating to elevated stress states. Pearson’s correlation revealed associations between RM and physical properties: positive with sand content and negative with clay content and optimum moisture content. Kruskal–Wallis tests confirmed RM's significant dependence on geotechnical variables, whereas PD showed no statistically significant with these factors. These findings underscore the importance of integrated physical–mechanical characterization for predicting the structural performance of LG’ soils. Furthermore, they highlight PD’s high variability and the necessity for global analyses to achieve more representative estimates in mechanistic–empirical pavement design.

Resumo em Inglês:

Abstract Several predictive models have been proposed in the literature to estimate soil-water characteristic curves (SWCCs) using basic soil properties. However, most of these models were not originally calibrated for tropical soils, such as bimodal materials commonly found in Brazil. To assess the applicability of some of these models to Brazilian tropical soils, which often present fine-particle cementation and lateritic behavior, this study evaluates four physico-empirical approaches: Arya & Paris (1981), Arya & Dierolf (1989), Aubertin et al. (2003), and Wang et al. (2017). A database containing information on 95 Brazilian soils was compiled and used as the basis for the analysis. The results showed that, in their original form, none of the evaluated models consistently represented the SWCCs of these soils with sufficient accuracy. Due to the models’ poor performance, specific geotechnical concepts not incorporated in the original formulations were examined and found to significantly influence the predictions. This analysis revealed that the Arya & Paris (1981) model holds promising potential for estimating the SWCC, provided that particle aggregation is addressed by combining grain-size distributions obtained under different dispersion states. Accordingly, this article proposes guidelines for the enhanced application of the Arya & Paris (1981) model in Brazilian geotechnical contexts, with the aim of improving predictive accuracy and broadening its applicability.

Resumo em Inglês:

Abstract Dynamic Load Test (DLT) on piles has been used as an alternative to Static Load Test (SLT), offering cost savings and time reduction. Sensors at the pile top capture signals during the hammer impact. These signals are analyzed using the Signal-Matching Method to adjust calculated curves to measured data, varying parameters such as shaft friction and toe resistance. Different solutions may yield good Match Quality (MQWU). In CAPWAP, quality is traditionally assessed through MQWU, indicating the error between measured and calculated curves. Historically, DLT and SLT correlate well through the Davisson Method. However, Murakami (2015, 2019) observed discrepancies between simulated load vs. displacement curves of CAPWAP and SLT, introducing the Match Quality of Settlements (MQS) to enhance the Physical Meaning of the analysis. Improving MQS also enhances MQWU, achieved by the determination of the pile shaft quake along with two boundary conditions, constituting a New CAPWAP Procedure, resolving the variability of results uniquely. This paper explores the concepts of Physical and Mathematical Meaning in DLT and their impact on the execution and interpretation of CAPWAP.

Resumo em Inglês:

Abstract Landslides constitute a recurrent natural hazard globally, severely impacting socio-economic and environmental systems. In Brazil, and particularly in the road infrastructure of Rio Grande do Sul, this vulnerability was dramatically evidenced by the extreme events of 2024. This study addresses the instability of 43 rock slopes along the BR-470 highway in the Serra das Antas region (between Bento Gonçalves and Veranópolis), a critical area with a history of rainfall-induced landslides structurally controlled by brittle discontinuities (columnar and sub-horizontal joints). The core objective was to perform a detailed geological-structural mapping of the Serra Geral Formation basaltic rock masses to diagnose instability patterns and define optimized intervention protocols. The methodology employed an integrated approach, combining detailed field geological-geotechnical mapping with kinematic and geomechanical analyses (limit equilibrium via Mohr-Coulomb and Hoek-Brown criteria). A geological-geotechnical compartmentalization of the rock masses was developed to reflect the complex structural heterogeneity, and the rock mass quality was assessed and classified using the GSI and RMR indices. Structural and kinematic analysis confirmed the prevalence of instabilities conditioned by these discontinuities, resulting in rockfall as the dominant failure mechanism (93% of cases), frequently associated with wedge failure (61%). The proposed stabilization solutions — including high-tensile steel mesh with anchored bolts and dynamic barriers — replace the traditional homogeneous treatment with a compartmentalized approach. It is concluded that compartmentalization constitutes an effective model, allowing technical and economic adjustments of the interventions to the specific geomechanical conditions of each segment, thereby increasing the reliability of the results and enhancing road safety.

Resumo em Inglês:

Abstract This study investigates the behavior of four unreinforced embankments on soft soils through numerical and parametric analyses. The embankments, composed of granular material, are 3.5 m in height and 17 m in width, and are modeled over a clay layer extending 30 m horizontally, with thicknesses of 5, 10, 15, and 20 m. The soft soil was simulated with the modified Cam Clay model, and the embankment fill with the Mohr–Coulomb criterion. Forty Abaqus simulations were performed, varying soil thickness, overconsolidation ratio (OCR), recompression index (κ), and critical state line slope (M). The analyses evaluated settlement, horizontal displacement, pore pressure, effective vertical stress and mobilized soil volume, applying multiple normalization approaches. Results highlight the strong influence of soil thickness and κ on deformation and pore pressure, the limited effect of M and OCR for thicker layers and confirm the usefulness of mobilized volume criteria for stability evaluation.

Resumo em Inglês:

Abstract During fracture propagation in quasi-brittle materials such as rock, stress concentration plays a critical role as a result of stress redistribution, leading to elevated stress levels near crack tips. In classical elastic analytical solutions, stresses at the crack tip tend toward infinity; therefore, conventional elastic analyses are inadequate for describing fractured materials. This study employs Linear Elastic Fracture Mechanics (LEFM) to model this phenomenon in rock, with a focus on representing mode I fracture toughness (KIc). To address these processes, the Continuum Voronoi Block Model (CVBM) is utilized. CVBM is a pseudo-discontinuum approach implemented within a Finite Element Analysis (FEA) framework, combining Voronoi tessellation and the Goodman joint, to represent the rock’s mesoscale structure. The model is first calibrated for deformational properties and tensile strength, and then iteratively adjusted to reproduce experimental KIc values. The calibration is validated under different boundary conditions through numerical simulations of Center-Cracked Tension (CCT) tests, Cracked Straight-Through Brazilian Disc (CSTBD) tests, and Semi-Circular Bending (SCB) tests, successfully reproducing fracture paths and yielding KIc values consistent with the literature.

Resumo em Inglês:

Abstract In recent years, Brazil has experienced a growing frequency of natural disasters, particularly those triggered by intense rainfall and unregulated urban expansion in geotechnically vulnerable areas. This scenario highlights the urgent need for educational and participatory strategies aimed at disaster risk reduction and the promotion of resilient communities. This article presents a case study of the Geotechnical Study Group (GEGEO), an outreach initiative based at the Federal University of Paraná (UFPR), which developed a series of actions between 2020 and 2023 to raise awareness about geotechnical and environmental risks. The initiatives included a Massive Open Online Course (MOOC), in-person educational workshops, and participatory risk mapping in collaboration with public schools and local communities. The study employed a qualitative approach to analyze the effectiveness of these activities in fostering civic responsibility and disaster preparedness. Results indicate that participatory methodologies—grounded in dialogical education and contextualized technical knowledge—enhanced community engagement and contributed to the co-production of localized risk management tools. Moreover, the integration of teaching, research, and extension proved to be a powerful strategy for promoting socially engaged engineering education. The outcomes reinforce the relevance of university extension programs as instruments for risk mitigation, educational innovation, and community empowerment in areas exposed to geotechnical hazards.

Resumo em Inglês:

Abstract This study investigates the use of empirical formulas for the determination of the yield pressure of marine clays through the CPTU. One such formula is that of Kulhawy & Mayne, which has previously been analyzed by the author (Massad, 2010), who proposed a methodology for determining its empirical factor for soils with known stress history and with cone resistance (qt) varying linearly with depth. These conditions have been observed in marine clays in Brazil and abroad. In the present work the author extends this methodology to two other formulas of Mayne (2017), which make use of cone resistance (qt), pore water pressure (u2) and hydrostatic pressure (uo), adjusting the empirical factors for cases of linear relationships of qt and u2 with depth. An analysis is conducted to identify the conditions necessary for these formulas to consistently produce the same yield pressure. The effectiveness of the proposed approach is demonstrated through three case studies, which include two European marine clays and one Brazilian marine clay, supported by CPTU data, specific unit weights, oedometer tests, and geological history.

Resumo em Inglês:

Abstract The design of fibre-reinforced concrete structures must follow the design principles concerning limit states, similar to those adopted for conventionally reinforced concrete. However, the use of linear elastic analysis or conventional yield-line theory may, in many cases, underestimate the benefits of fibres in providing greater load-bearing capacity, particularly when high-performance steel fibres are adopted. This paper presents two case studies of real tunnel projects in which the author was involved, where the use of non-linear modelling of steel fibre-reinforced concrete elements, coupled with physical testing, provided significant benefits in the design and construction of tunnel linings. The first case focuses on the design of thin tunnelling linings using rock-bolted shotcrete. In this case, the non-linear modelling coupled with full-scale field tests demonstrated load-bearing capacities up to 6-7x greater than conventional design methods. The second case presents the design of a segment lining and the effects of fibre reinforcement on the bursting and splitting capacity of longitudinal joints under rotation. In this case, non-linear modelling coupled with laboratory testing on large-scale segment joint samples demonstrated that conventional reinforcement was unnecessary, whereas analysis with linear-elastic theory indicated otherwise.

Resumo em Inglês:

Abstract Shallow geothermal systems based on ground source heat pumps constitute an energy-efficient solution for space heating and cooling; however, their application in Brazil remains limited, particularly with respect to horizontal ground heat exchangers installed in residual soils. This paper presents a case study on the analytical design of a horizontal Slinky-type ground heat exchanger intended for the thermal conditioning of a 25 m2 experimental test room located in Maringá, Paraná, southern Brazil, operating approximately 40 h per week. The subsurface profile is composed of residual clayey soil derived from basaltic bedrock, whose geotechnical and thermal properties were determined through laboratory and in situ investigations. The design was carried out using an analytical methodology specifically developed for horizontal geothermal systems, which accounts for seasonal ground temperature variations, soil thermal conductivity and diffusivity, and peak building thermal loads. The results reveal a pronounced asymmetry between operating modes, with a required pipe length of approximately 306 m for summer cooling and 126 m for winter heating. A compact horizontal Slinky configuration was adopted to satisfy site constraints while maximizing heat exchange per unit area. Sensitivity analysis indicates that soil thermal conductivity is the dominant parameter governing exchanger length, followed by thermal diffusivity and heat pump performance. The findings highlight the importance of site-specific thermal characterization and the use of appropriate design methodologies for horizontal geothermal systems in subtropical and residual soil environments.

Resumo em Inglês:

Abstract Textured high-density polyethylene (HDPE) geomembranes are widely used as liners in environmental containment systems, particularly in mining facilities and sanitary landfills. Their textured surfaces enhance interface friction, improving the mechanical stability of geosynthetic barrier systems. This article presents a comprehensive review of their applications, interface behavior, and long-term performance, with emphasis on durability. Key manufacturing processes and technological advances, including conductive, Ethylene Vinyl Alcohol (EVOH), and colored layers, are discussed. Beyond manufacturing aspects, installation quality is also addressed, emphasizing that proper welding procedures, certified installers, and field quality control are essential to ensure long-term performance and minimize premature failures. Although various texturing methods are employed, the literature still lacks systematic comparative studies that isolate variables such as asperity height, which limits understanding of how manufacturing processes influence interface behavior. Furthermore, recent findings suggest that surface texturing, depending on material formulation and exposure conditions, may accelerate antioxidant depletion, potentially affecting service life. Field exposure and exhumation studies remain scarce, yet they are fundamental for validating laboratory predictions and refining design approaches. The findings highlight the need for standardized testing protocols and long-term studies tailored to the environmental conditions under which textured HDPE geomembranes are exposed. Overall, the information presented herein provides both scientific insight and practical guidance for the selection of materials and installation practices that ensure the long-term durability of geotechnical and environmental barrier systems.