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Open research questions in Geotechnical Engineering and Soil Mechanics

72 unresolved questions extracted from the limitations and future-work sections of 538 Geotechnical Engineering and Soil Mechanics papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • The complex interaction between sand and clay particles affects the compression behavior of sand-clay mixtures. The limited understanding of the formation mechanism of the coarse-grained skeleton in sand-clay mixtures. The difficulty in replicating the properties of in-situ soils in laboratory-prepared specimens.

    Effects of sand content and grain size on the compression behaviour of clayey sand · 2026 · DOI

  • The compressibility of sand-clay mixtures remains limitedly understood, particularly regarding the influence of sand particle size. Traditional compression theory has limitations in assessing the compressibility of sand-clay mixtures.

    Effects of sand content and grain size on the compression behaviour of clayey sand · 2026 · DOI

  • Future studies can investigate the performance of pile raft foundations in different soil conditions. The machine learning models developed in the study can be improved and applied to real-world scenarios. The study's findings can be used to design more efficient pile raft foundations.

    Experimental and predictive analysis of pile raft foundation in clayey soils using machine learning and MATLAB tools · 2026 · DOI

  • There is a lack of studies investigating the performance of pile raft foundations in clayey soils. The existing literature does not provide a clear understanding of the factors influencing the performance of pile raft foundations. The study aims to fill this gap by investigating the performance of pile raft foundations in clayey soils.

    Experimental and predictive analysis of pile raft foundation in clayey soils using machine learning and MATLAB tools · 2026 · DOI

  • The complex and variable geological conditions on the seabed - The risk of punch-through failure - The need for accurate simulation of the piling and penetration behavior of jack-up offshore platforms

    Experimental study on piling and penetration behavior of jack-up offshore platforms on layered seabed foundations · 2026 · DOI

  • Pronounced subjectivity and limited repeatability of the standard thread-rolling test. Complexity of determining the plastic limit. Need for a standardised, mechanical, more reliable and reproducible method.

    Determining the plastic limit of soil using the fall cone test and undrained shear strength · 2026 · DOI

  • High cost and extended testing duration of static load testing. Limited applicability of dynamic testing methods to different soil types and pile configurations. Sensitivity of signal-matching analysis to modeling assumptions.

    CORRELATING PILE DRIVING ANALYZER (PDA) AND CASE PILE WAVE ANALYSIS PROGRAM (CAPWAP) RESULTS TO INFER SUBSURFACE SOIL VARIABILITY: A CASE STUDY ON DRIVEN SPUN PILES · 2026 · DOI

  • The complex system geometry of geogrid-reinforced stone columns. The uncertainties surrounding the influencing parameters. The need for an accurate and reliable predictive model.

    Predicting Ultimate Bearing Capacity of Geogrid-Reinforced Stone Columns Using Hybrid Neural Networks and Harris Hawks Optimization · 2026 · DOI

  • Existing research and engineering practice continue to focus primarily on pier scour, while comparatively limited information is available for contraction and abutment scour in cohesive soils and rock formations.

    A Review on Bridge Scour Analysis in Cohesive Soils and Scour-Susceptible Rocks · 2026 · DOI

  • Certain parameters relating to the weak rock could not be determined from the available rock quality designation and the uniaxial compressive strength.

    Back-analysis of bi-directional pile load tests of drilled shaft socketed in weak rock · 2026 · DOI

  • However, interpreting PMT data for constitutive parameters remains reliant on empirical correlations, and a key challenge is the poorly understood size effect arising from the equipment dimensions.

    Numerical Simulation of Size Effects of Laboratory Pressuremeter Tests · 2026 · DOI

  • However, existing studies have primarily focused on immersion-induced collapsibility, while the effects of seismically induced loess subsidence remain insufficiently understood and inadequately represented in current analytical models.

    Analytical Solution for Negative Skin Friction of Pile Foundations Induced by Seismic Loess Subsidence · 2026 · DOI

  • The experimental findings of the presented work indi- cate that the localised behaviour of grain displace- ments as well as grain rotations in the miniaturised direct shear test also lead to localisations of changes in the initial capillary state. The pronounced grain rotations and contact changes in the shear zone, lead- ing to a reduction in coordination number due to dila- tancy, increase the number of contacting independent water clusters and reduce the wetted surface area of sand grains also in these zones. These findings are based on a neighbourhood analysis counting each dis- crete grain’s neighbour voxels during the shear pro- cess. While the data of these variables shows robust trends, further studies should investigate a possi- ble resolution dependence of these measures, i. e., a dependence on voxel size. As suction is not measured in the current design of the presented experiment, fur- ther research should investigate local suction changes, e. g., by studying local changes in mean curvature (Milatz et al. 2022) in highly-resolved CT images. Furthermore, the role of the suction and saturation changes with regard to local changes of capillary cohesion need to be investigated in future studies. Acknowledgements The support given by the colleagues at Laboratoire 3SR, Gioacchino Viggiani, Nicolas Lenoir, and Pascal Charrier, is greatly acknowledged. We also thank the spam developers who have boosted our analysis during an inspiring software workshop held in the French Alps in Octo- ber 2024. Author contributions M.M. is responsible for the whole work presented in this manuscript, including experimenting, data analysis and writing. Funding Open Access funding enabled and organized by Projekt DEAL. The authors have not disclosed any funding. Data availability The image data as well as measurements from the direct shear test referred to in this paper are shared with the scientific community in Milatz (2026).

    Grain and Pore Scale Insights into Direct Shearing of Partially Saturated Sand · 2026 · DOI

  • The sub-stepping convergence behavior shown in Table 6 indicates variable activation of sub-stepping across different lift percentages (0-32 sub-steps for some conditions, 0 for others). The criteria governing when sub-stepping is triggered and optimal sub-step sizing strategies for minimizing computational cost while maintaining accuracy are not explicitly characterized.

    Implicit sub-stepping scheme for critical state soil models · 2026 · DOI

  • The numerical validation of the implicit sub-stepping scheme is limited to three excavation case studies (tunnel excavation, NATM excavation, TBM excavation). Testing under diverse loading conditions—such as undrained cyclic loading, anisotropic consolidation paths, and varying initial void ratios—is needed to fully validate the algorithm's robustness across the stress space covered by critical state models.

    Implicit sub-stepping scheme for critical state soil models · 2026 · DOI

  • Traditional piles with uniform cross-sections are an important part of geotechnical engineering, Researchers have always wanted to improve their load-bearing capacity by modifying the shape of the pile. During this process, the development of modern designs has promoted the use of wedge-shaped piles, bell-shaped piles, and branched piles. Because of these, screw piles become prominent. The development of screw piles in the latter half of the 19th century, as discussed by Perko 6, was a major advancement. The modern screw pile, which has a threaded lower segment and a cylindrical top, presents distinct advantages, including a high load-bearing capacity, excellent adaptability to various soil conditions, and low noise and vibration during installation, making it more popular in densely populated or environmentally sensitive areas. Figure 1 presents the various components and definitions of a screw pile. ARTICLE IN PRESS ARTICLE IN PRESS ACCEPTED MANUSCRIPT ARTICLE IN PRESS (a) (b) (c) Fig. 1. Screw pile components and definitions: (a) components of a pile; (b) design parameters; (c) definitions of screw pile. They are favored for high-rise foundations due to lower downdrag force compared to conventional piles, as the shaft diameter is smaller than the helix diameter 7, 8, 9, 10. Installation involves hydraulic torque motors, with helices penetrating the soil 11, 12, 13. Grouting, as recommended by Livneh and Naggar 14, boosts buckling resistance and load capacity, making screw piles more effective; ungrouted screw piles have half the bearing capacity of grouted ones 15. Crowding ensures that the piles reach adequate depths without exceeding the torque capacity 16 17. The load transfer to the soil is influenced by soil strength, with screw plates bearing more load than the shaft 18,19. Nasr 20 highlighted that the pile installation process should be considered in the methodology process due to the impacts of soil stress conditions. Furthermore, Lee et al. 21 showed that the lateral capacity of the pile decreases when simultaneous vertical loading is applied. Alexander Mitchell introduced the idea to strengthen building foundations in 1836, and at that time, the concept of screw piles was developed. Subsequently, simple structural innovation technology evolved into a broadly applicable solution for a wide range of geotechnical applications. Screw piles are now employed to resist both compressive and lateral forces, offering advantageous such as rapid installation, reusability, and minimal dewatering requirements.

    Bearing mechanism and design optimization of screw piles in loess area · 2026 · DOI

  • The limited quantity of experimental data obtained from laboratory triaxial tests poses a significant constraint. The study uses a finite element model to simulate loess triaxial shear tests under various conditions to overcome this limitation.

    Prediction of loess shear strength using triaxial test and artificial neural network · 2026 · DOI

  • Further investigation of the influence of other material parameters on shear strength. Development of more advanced models to predict loess shear strength. Application of the proposed method to other types of soils.

    Prediction of loess shear strength using triaxial test and artificial neural network · 2026 · DOI

  • Further studies can investigate the influence of other factors on maximum shear stiffness, such as particle shape and size distribution. The predictive formula can be validated against additional experimental data.

    Study on the macro-micro influence of gradation area on the maximum shear stiffness of coarse-grained soils · 2026 · DOI

  • Traditional methods for determining bearing capacity factors are complicated and involve lengthy calculations. There is a need for a simple and efficient method to estimate Nq.

    Bearing Capacity Factor Nq Estimation of Pilani Soil Using Ultrasonics · 2026 · DOI

  • The lack of a reliable method for predicting cyclic resistance of sands with non-plastic fines. The need for a density measure that effectively normalizes fines effects in silty sands.

    A machine learning framework for evaluating cyclic resistance of sands with non-plastic fines · 2026 · DOI

  • The dataset lacks sufficient information on sample preparation methods and soil classification indices. The model may not be applicable to diverse soil types.

    A data-driven technique for predicting the triaxial behaviour of soils · 2026 · DOI

  • The key findings reveal that: (1) cyclic loadings considerably change anchor holding capacity and evolution of seabed trenching, yet most existing design methods still use quasi-static loads; (2) site-specific data from integrated geophysical–geotechnical surveys are vital to reduce uncertainty in anchor penetration and the frictional resistance of chains; (3) geohazards, such as shallow gas, marine landslides, and seabed erosion, pose under-recognized risks to long-term anchor reliability.

    Seabed–Mooring Interaction for Offshore Wind Energy Systems: A Scoping Review · 2026 · DOI

  • Existing models for predicting the resilient modulus of subgrade soils have limitations. The models cannot predict modulus values within the no-dynamic stress zone. There is a need for a comprehensive methodology for determining the resilient modulus of subgrade soil under a wide range of stress states.

    Characteristics of subgrade soil resilient modulus considering wide-range stress state · 2026 · DOI

  • The need for a comprehensive assessment of soil liquefaction hazard in Osmaniye, Türkiye. The lack of detailed studies on the spatial and depth-dependent liquefaction potential in the region.

    Assessment of soil liquefaction hazard using the liquefaction potential and severity index in Osmaniye, Türkiye · 2026 · DOI

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72 open questions have been extracted from the limitations and future-work passages of 538 Geotechnical Engineering and Soil Mechanics papers in our library. Each one below links back to the study that raised it, so you can read the original claim in context.

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