Journal of Geotechnical and Geoenvironmental Engineering

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ISSN / EISSN : 1090-0241 / 1943-5606
Total articles ≅ 5,011
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Masood Abdollahi,
Journal of Geotechnical and Geoenvironmental Engineering, Volume 147; https://doi.org/10.1061/(asce)gt.1943-5606.0002605

Abstract:
Unsaturated expansive soils annually cause major economic losses and structural damages to foundations and earthen structures, primarily due to exhibiting large amounts of swelling and shrinkage when subjected to variations in water content. If an expansive soil is laterally constrained, lateral swelling pressure can exacerbate the unfavorable characteristics of expansive soil by increasing the lateral earth pressure applied to geotechnical structures. This study presents a model to determine lateral swelling pressure considering transient flow in deformable (swelling) unsaturated soils. The transient profiles of water content and suction versus depth during the wetting process are determined considering a coupled hydromechanical behavior. The interplay between the soil deformation, water content, and hydraulic conductivity is accounted for by linking the soil swelling-shrinkage characteristic curve (SSSCC), the soil water retention curve (SWRC), and the hydraulic conductivity function (HCF). An analytical model for quantifying lateral swelling pressure is then developed using a suction stress-based effective stress, the SWRC, and extended Hook’s law for unsaturated soils. The presented model is built upon the conceptual model that lateral swelling pressure is controlled by infiltration-induced changes in suction stress of a laterally-constrained unsaturated soil. The model offers a generalized framework to determine lateral swelling pressure of expansive soils under different degrees of saturation while accounting for the effect of deformation on water content and suction profiles. The model is validated against results attained from three sets of experimental tests available in the literature. Through the three case studies examined, the proposed model exhibited a reasonable accuracy over a wide range of degrees of saturation from 50% to near fully saturated conditions. The findings of this study can contribute toward more accurate evaluations regarding the performance of geotechnical structures in unsaturated expansive soils.
Farzad Kaviani-Hamedani, , Ali Lashkari
Journal of Geotechnical and Geoenvironmental Engineering, Volume 147; https://doi.org/10.1061/(asce)gt.1943-5606.0002622

Abstract:
Continuous bidirectional shear wave velocity measurements were performed in the vertical (V) and horizontal (H) directions to characterize fabric evolution of triaxial soil specimens during shear, wherein, in addition to the vertical direction, two specially designed horizontal bender elements’ housings were mounted on samples using a new measurement technique. The specimens were prepared using moist tamping and water sedimentation methods and then subjected to strain-controlled triaxial compression shear under drained condition. Different sets of stress paths were applied to uncover the evolution of fabric during consolidation and shearing. The magnitudes of the shear wave velocities in different directions highlighted severe soil anisotropy at the critical state. It was found that the shear wave velocities were governed by void ratio, effective stress, and sand fabric. Interpretation of results shows the limited accuracy of the conventional empirical functions to predict the initial shear modulus in the consolidation stage. A fabric function taking into consideration the role of the soil fabric on soil elastic moduli was proposed, and its variations were traced during shear. Variations of the fabric function underline that there exists a unique anisotropic fabric at the critical state.
Julian Asdrubal Buritica Garcia, , Danilo Vítor dos Santos Mützenberg, Bernardo Caicedo, Gilson de Farias Neves Gitirana
Journal of Geotechnical and Geoenvironmental Engineering, Volume 147; https://doi.org/10.1061/(asce)gt.1943-5606.0002649

Abstract:
The rigid inclusion technique has been used worldwide to reinforce soft soil for road and railway embankments and deep building foundations. This technique is studied through field tests and physical and numerical models. Most studies focus on embankments or slabs on soils reinforced with rigid inclusions. Previous research based on numerical modeling demonstrated that the load-transfer mechanisms for a rigid slab differ from those for an embankment. Here, a simplified physical model was developed to assess the load-transfer mechanism between the inclusion head and the load-transfer platform (LTP) under a rigid slab. This research focused on the use of an alternative material for the LTP, which is a compacted soil with or without cement. When the reinforced soil contribution is neglected, the LTP weight and applied load are transmitted completely to the inclusion cap (load-transfer efficiency of 100%). As the LTP material stiffness increases, the settlement magnitude decreases considerably. The experiments demonstrated that the applied load was transferred to the inclusion head through an inverted truncated load-transfer cone (LTC) over the inclusion; the external angle depended on the LTP material strength in accordance with Coulomb’s theory. The principal stress state at the base of the LTC also was determined. Equations are proposed to determine LTP thickness and inclusion spacing.
Juntao Wu, M. Hesham El Naggar,
Journal of Geotechnical and Geoenvironmental Engineering, Volume 147; https://doi.org/10.1061/(asce)gt.1943-5606.0002636

Abstract:
This paper investigates the dynamic response of soil around a laterally vibrating extended pile shaft and its application to the lateral parallel seismic (PS) integrity testing method. Considering the high pile to soil relative stiffness ratio, a new analytical model is proposed incorporating an extended half-space soil model excited by the laterally vibrating pile. The developed equations of the analytical model are solved by employing the Fourier-Hankel integral transform. This scheme avoids the complicated pile–soil coupling analysis while maintaining high accuracy. The developed model and its analytical solution are then utilized to verify the applicability of the lateral PS method to predict the unknown pile length. The effects of pile and soil properties on the soil dynamic response and technical aspects of the PS test are investigated through a comprehensive parametric study. The obtained results demonstrate that the lateral PS test could be successfully used in practice to overcome the limitations of the low-strain pile integrity test (PIT).
Khoa M. Tran, , Giang D. Nguyen
Journal of Geotechnical and Geoenvironmental Engineering, Volume 147; https://doi.org/10.1061/(asce)gt.1943-5606.0002633

Abstract:
Desiccation cracking in clayey soils occurs when they lose moisture, leading to an increase in their compressibility and hydraulic conductivity and hence a significant reduction of soil strength. The prediction of desiccation cracking in soils is challenging due to the lack of insights into the complex coupled hydromechanical process at the grain scale. In this paper, a new hybrid discrete-continuum numerical framework, capable of capturing hydromechanical behavior of soil at both grain-scale and macroscale, is proposed for predicting desiccation cracking in clayey soil. In this framework, a soil layer is represented by an assembly of discrete element method (DEM) particles, where each occupies an equivalent continuum space and carries physical properties governing unsaturated flow. These particles move freely in the computational space following the DEM, and their contact network and the continuum mixture theory are used to model the unsaturated flow. The dependence of particle-to-particle contact behavior on water content is represented by a cohesive-frictional contact model, whose material properties are governed by the water content. In parallel with the theoretical development is a series of experiments on three-dimensional (3D) soil desiccation cracking to determine essential properties and provide data for the validation of mechanical and physical behavior. Very good agreement in both physical behavior (e.g., evolution of water content) and mechanical behavior (e.g., occurrence and development of cracks, and distribution of compressive and tensile strains) demonstrates that the proposed framework is capable of capturing the hydromechanical behavior of soil during desiccation. The capability of the proposed framework facilitates numerical experiments for insights into the hydromechanical behavior of unsaturated soils that have not been possible before.
, Heyue Zhang, Jun Liu, Ying Huang
Journal of Geotechnical and Geoenvironmental Engineering, Volume 147; https://doi.org/10.1061/(asce)gt.1943-5606.0002625

Abstract:
Jack-up leg installation, extraction, and reinstallation near extraction-induced footprints are simulated using the coupled Eulerian-Lagrangian method with a strain-softening soil model. A typical footprint considering soil remolding is summarized based on 29 installation and extraction simulations. The reinstallation behavior of flat-base footings, spudcans, and skirted footings near extraction-induced and idealized conical or cylindrical footprints is compared. The horizontal force and bending moment induced by the footprint are explained in terms of predicted soil flow mechanisms and reaction loads acting on various footing surfaces. Considering soil remolding in a footprint, the results indicate that the soil on the near side of the footprint collapses earlier than that on the far side. The back flow soil on the near side of the footprint leads to obvious negative H loading on the footing leg. Two peaks in the M profile are observed. The first one is due to the footing touching the uneven seabed and the second is due to asynchronous collapse of the near-side and far-side walls of the footprint. The effects of the footing type and offset distance on the reinstallation behavior are discussed. The maximum values of H and M in both the positive and negative ranges during reinstallation are presented. Among the investigated footing types, the skirted footing has the greatest potential for mitigating the footing–footprint interaction problem because it provides the largest vertical resistance but induces the smallest horizontal forces and bending moments.
, Yifan Tang, Guoliang Ma, John S. McCartney, Jian Chu
Journal of Geotechnical and Geoenvironmental Engineering, Volume 147; https://doi.org/10.1061/(asce)gt.1943-5606.0002621

Abstract:
This paper includes an investigation of the thermal conductivity of biocemented soils to better understanding the regimes of heat transmission through soils treated by microbially induced calcium carbonate precipitation (MICP). A series of thermal conductivity tests using the transient plane source method (TPS) was performed on biocemented silica sand specimens with different gradations, void ratios, and MICP treatment cycles. The results showed that MICP treatment greatly improved the thermal conductivity of sand specimens. An increase in uniformity coefficient or a decrease in void ratio of the sand resulted in an increase in the thermal conductivity of MICP-treated specimens for a given MICP treatment cycle. The increment of thermal conductivity of MICP-treated specimens with respect to that of untreated specimens was also affected by gradation, void ratio, and content of calcium carbonate. The greatest improvements in thermal conductivity were achieved for sands having an initial degree of saturation between 0.82 and 0.85. An empirical equation was established to predict the thermal conductivity of MICP-treated silica sand with different variables, which may be useful in designing energy piles in biocemented sand layers.
, Abdelmalek Bouazza, John S. McCartney
Journal of Geotechnical and Geoenvironmental Engineering, Volume 147; https://doi.org/10.1061/(asce)gt.1943-5606.0002640

Abstract:
This paper examines the effects of monotonic and cyclic temperature changes of a model energy pile (diameter=25 mm, length=264 mm) on the variations in temperature and volumetric water content of surrounding unsaturated sand. Water flowed away from the pile during heating to 36°C and toward the pile during cooling to 5°C, causing soil drying and wetting near the pile, respectively. The change in volumetric water content was time-dependent, nonlinear, and slower than the change in soil temperature and continued to evolve after the soil temperature changes stabilized. Cyclic heating/cooling induced lower thermohydraulic changes in the soil than monotonic heating and cooling. The most significant changes in soil temperatures and volumetric water content were closest to the pile at a radial distance of 20 mm from the edge of the pile and reduced with increasing radial distance for all cases. The largest change in the degree of saturation was near the pile and was up to 6% for monotonic heating. Cyclic heating/cooling induced irreversible cyclic hydraulic responses near the pile with consecutive thermal cycles and caused a permanent reduction in the soil volumetric water content. However, these irreversible cyclic effects were dominant at a radius of 20 mm and reduced with increasing radial distance from the energy pile. The change in volumetric water content was time-dependent, indicating that the ratio of heating to cooling times during cyclic heating/cooling will have a significant effect on the reversibility of hydraulic responses under temperature cycles.
, Mello C. Papadopoulou, Mark F. Randolph
Journal of Geotechnical and Geoenvironmental Engineering, Volume 147; https://doi.org/10.1061/(asce)gt.1943-5606.0002606

Abstract:
Recent research on the topic of pile base resistance has demonstrated that the guidelines provided by existing design manuals and codes are rather conservative in the case of clayey soils under undrained conditions. With the aim of investigating this topic more rigorously, a computationally intensive study was carried out to quantify the effect of the soil rigidity index on the response of pile base resistance. A precise assessment of the results led to the formulation of hyperbolic relationships that capture the development of the base resistance as a function of settlement. The relationships were implemented in a beam column analysis and validated against a full axisymmetric numerical analysis and also with respect to field data from a pile test performed using an Osterberg cell near the pile base. The validation process demonstrated the usefulness of the method and recommendations arising with respect to mobilization of the pile base resistance. This study should, therefore, assist in the development of more scientifically based guidelines for pile design that balance safety and economy.
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