This study provides a comprehensive analysis of the undrained failure envelope for spudcan foundations in anisotropic clays using the AUS failure criterion as the soil strength model. The influence of embedment depth (L/D) and anisotropic strength (re) on spudcan behaviour under combined loading conditions is investigated. Failure envelopes are derived through three-dimensional finite element limit analysis (3D FELA) in both (H/ suTCA, M/suTCAD) and (V/Vult, H/suTCA, M/suTCAD) spaces. The study also illustrates spudcan foundation failure mechanisms, providing valuable insights for designing footings in anisotropic clays under combined loads (V, H, M). Additionally, an innovative soft-computing approach is introduced: a machine learning model that integrates categorical boosting (CatBoost) with the flower pollination algorithm (FPA) for optimized predictions of the spudcan failure envelope. The proposed FPA-CatBoost model is validated against numerical FELA results, demonstrating a strong correlation and offering engineers a reliable tool for determining spudcan foundation failure envelopes under varied loading conditions.

This paper provides a comprehensive analysis of the undrained failure envelope for embedded foundations in anisotropic clays. Using the AUS failure criterion as the soil strength model, the study examines how the anisotropic strength (re) and embedment depth (D/B) affect the behavior of the footing under combined loading conditions. Failure envelopes are assessed via two-dimensional finite element limit analysis (2D FELA) in both 2D and 3D spaces. This research highlights the failure mechanisms of embedded foundations, offering valuable insights into the engineering design of footings in anisotropic clays subjected to combined loads (V, H, M). Furthermore, this study introduces an advanced soft-computing approach by creating a machine learning model that leverages the adaptive neuro-fuzzy inference system (ANFIS) integrated with the particle swarm optimization (PSO) algorithm to predict the failure envelope of embedded footings, highlighting the novelty and original of this study. The optimised ANFIS model has been validated and demonstrates a strong correlation with the numerical FELA results, offering engineers a valuable tool for determining the failure envelope of embedded foundations in anisotropic clay under different loading scenarios (V, H, M).

The synergetic effects of alkaline red mud (RM) and sulfate-based phosphogypsum (PG) on the undrained triaxial behavior of cement-admixed clay were explored in this study. A series of isotropically consolidated undrained triaxial tests were performed on stabilized clay with respect to different admixed RM/PG proportions. The triaxial behavior of stabilized clay is presented in terms of a stress-pore pressure-strain relationship, failure mode, undrained deformation modulus, stress path, and failure envelope. Scanning electron microscopy (SEM) tests were conducted to survey microscopic evolution. The results showed that the brittleness of the specimen intensified with a high RM content, which was manifested by a predominant postpeak strength reduction. As the PG content increased, the strain-softening behavior weakened and gradually evolved into strain-hardening. The failure mode changed from local shear failure to the single cone failure and bulging failure correspondingly. The RM played a role in increasing soil cohesion, whereas PG contributed to a larger frictional angle at the postyield stage. Microscopic observations indicated that the alkali source from RM significantly promoted pozzolanic reactions and strengthened cementation bonds, which increased the peak strength, deformation modulus, and cohesion. In addition, the sulfate in PG contributed to ettringite generation among clay particles and clusters, resulting in a more ductile behavior and a larger frictional angle due to large clusters formed.

This paper proposes a new method for computing the undrained lateral capacity of Reinforced Concrete (RC) piles in cohesive soils, overcoming inherent conservativeness of classical Broms' theory. The proposed method relies on a new theoretical distribution for the limiting soil resistance, simple enough to derive closed-form solutions of the undrained lateral capacity, for different restraints at the pile head and for all possible failure mechanisms. After validation against numerical results and experimental data, the model is used to compute the failure envelope of RC piles under generalised loading. 3D FE analyses are used as benchmark to identify the main factors governing the ultimate response of RC piles. To this purpose, the Concrete Damaged Plasticity model is adopted to reproduce nonlinear concrete behaviour, which is an essential ingredient when modelling pile behaviour under horizontal loading. FE analyses show that, contrary to what observed for rigid and elastic piles, the ultimate response of RC piles relies on the soil strength mobilised at shallow depths, where the normalised lateral soil resistance basically depends on the sole adhesion factor. The proposed solutions are readily applicable to the design of single piles, as well as to the computation of three-dimensional interaction domains of pile groups.

Several methods have been used over time to improve the mechanical properties of fine-grained soils. One of the recently introduced materials for soil stabilization is incinerated sewage sludge ash (ISSA). This material is a by-product of the wastewater treatment process that is usually disposed of during the treatment cycle. This paper investigated the effects of adding the optimum amount of ISSA and a mixture of ISSA with hydrated lime (IL) on the mechanical properties of dispersive fine-grained soil. The effects of curing time on the UCS was also evaluated. The Mohr-Coulomb failure envelope parameters of the mixtures were subsequently estimated based on the performed test results using the Consoli et al (J Mater Civ Eng 27(5):04014174, 2015) method which eliminates the need to perform triaxial tests. The results indicated that ISSA and IL can improve the mechanical characteristics of the dispersive soil effectively and that curing time was substantial for better performance of the treated soil. Finally, the application of the Consoli and others method to predict the failure envelope parameters of the treated soil was evaluated using triaxial tests. The comparison of the results proved the suitability of the proposed method to estimate the failure envelope parameters of the ISSA and IL-treated dispersive soil.

Given the critical role of true triaxial strength assessment in underground rock and soil engineering design and construction, this study explores sandstone true triaxial strength using data-driven machine learning approaches. Fourteen distinct sandstone true triaxial test datasets were collected from the existing literature and randomly divided into training (70%) and testing (30%) sets. A Multilayer Perceptron (MLP) model was developed with uniaxial compressive strength (UCS, sigma c), intermediate principal stress (sigma 2), and minimum principal stress (sigma 3) as inputs and maximum principal stress (sigma 1) at failure as the output. The model was optimized using the Harris hawks optimization (HHO) algorithm to fine-tune hyperparameters. By adjusting the model structure and activation function characteristics, the final model was made continuously differentiable, enhancing its potential for numerical analysis applications. Four HHO-MLP models with different activation functions were trained and validated on the training set. Based on the comparison of prediction accuracy and meridian plane analysis, an HHO-MLP model with high predictive accuracy and meridional behavior consistent with theoretical trends was selected. Compared to five traditional strength criteria (Drucker-Prager, Hoek-Brown, Mogi-Coulomb, modified Lade, and modified Weibols-Cook), the optimized HHO-MLP model demonstrated superior predictive performance on both training and testing datasets. It successfully captured the complete strength variation in principal stress space, showing smooth and continuous failure envelopes on the meridian and deviatoric planes. These results underscore the model's ability to generalize across different stress conditions, highlighting its potential as a powerful tool for predicting the true triaxial strength of sandstone in geotechnical engineering applications.

Flooding occurrences have become increasingly severe, posing a serious danger to end-user safety and bridge resilience. As flood fragility assessment is a valuable tool for promoting the resilience of bridges to climate change, it is of great importance to push the development of such methods. However, flood fragility has not received as much attention as seismic fragility despite the significant amount of damage and costs resulting from flood hazards. There has been little effort to estimate the flood fragility of bridges considering various flood-related factors and the corresponding failure modes. To this end, a fragility-based approach that can explicitly address the scour-hole geometry and flood-induced lateral load is presented. First, a three-dimensional finite-element model with pile foundations and surrounding soil was established to estimate the failure mode under various flood scenarios. The loadings on pile foundations were characterized by vertical loading from the superstructure, horizontal loading from the flood-induced lateral load, and the scour effect simulated through a time-history analysis. Then, all potential failure modes of bridge pile foundations in various flood scenarios were summarized. Based on extensive parameter investigations using the deterministic method, the dominant failure mode of penetration failure was determined, and a failure envelope was fitted to guide the design of the pile foundation. Upon establishing the failure mode, a probabilistic fragility analysis considering uncertainties in hydraulic, structural, and geological parameters was finally conducted using the Latin hypercube sampling (LHS) method. The results showed the effects of variation on the fragility of the pile foundation, highlighting that the deterministic analysis without considering the uncertainties in model parameters leads to underestimating the risk due to the penetration failure and the significant influence region.

Failure of trees in high winds is of interest to a broad array of stakeholders: foresters, meteorologists, homeowners, insurance industry, parks and recreation management. Equally broad is the array of disciplines that contribute to understanding windthrow failure of trees: aerodynamics, forest management sciences, biomechanics, tree biology, and geotechnical engineering. This paper proposes a mechanistic model for assessing the windthrow failure of trees from a geotechnical engineering perspective. The model assumes a homogenized tree root-soil structure enclosed within a cylindrical volume characterizing the root spread and depth. The model predicts the anchorage resistance of a soil-root system by estimating the uprooting resistance of an equivalent circular footing using a 3D load failure envelope with a rotated parabolic ellipsoid shape. The proposed model was validated using the UK Forest Research Tree Pulling Database (UTPD) with 1239 conifer trees of six common species. The results show that the model successfully predicts the windthrow resistance of various tree species and sizes for different soil states. The soil type and state significantly affected the uprooting resistance, with the effective soil unit weight and water table depth being key soil parameters controlling tree anchorage. Conversely, soil friction angle and soil cohesion have only a modest influence on tree anchorage. The influence of desaturation due to negative pore water pressures was also investigated and found to have a significant effect on the uprooting resistance. Although the model shows promise, the paper concludes that further improvements could be made in form and calibration, as discussed in the paper.