Self-boring pressuremeter (SBPM) tests are widely used in situ investigations, due to their distinct advantage to measure the shear stress-strain-strength properties of the surrounding soil with minimum disturbance. The measured pressuremeter curve can be interpreted using analytical solutions based on the long cylindrical cavity expansion/contraction theory with relatively simple constitutive models, to derive useful soil properties (e.g., undrained shear strength of clay, shear modulus, and friction angle of sand). However, the real soil behavior is more complex than the assumed constitutive relations, and the derived parameters may differ from those obtained using more reliable lab tests. In addition, SBPM tests can be affected by other well-known factors (e.g., installation disturbance, limited length/diameter ratio, and strain rate) that are not considered in the analytical solutions. In this paper, SBPM tests are evaluated using finite-element analysis and the MIT-S1 model, a unified constitutive model for soils, to consider complex soil behavior more realistically. SBPM tests in Boston Blue Clay and Toyoura sands are simulated in axial symmetric and plain strain conditions, and the computed results are interpreted following the suggested procedures by analytical solutions. The derived parameters are compared with those from the stress-strain relations to evaluate the reliability of SBMP tests for practical application.

Artificial ground freezing (AGF) is an effective technique for ground stabilization in projects such as tunneling and shaft mining. This study examines the impacts of freeze-thaw processes, soil type, and compaction levels on the strength characteristics of sandy and clayey soils and evaluates AGF performance through laboratory-scale physical modeling using liquid nitrogen as the cooling agent. Results indicate that freezing significantly enhances soil strength, but thawing leads to notable reductions. Sandy soils compacted to 95% experienced a 50% decrease in unconfined compressive strength (UCS) after brief exposure to thawing, while clayey soils exhibited a smaller reduction of 30%. Compaction emerged as a critical factor in strength retention, with UCS in sandy soils decreasing by 50% when compaction dropped from 95 to 85%, compared to a 25% reduction in clayey soils. The results also demonstrated that sandy soils froze more rapidly and efficiently, achieving a frozen diameter of approximately 25 cm around a single freezing pipe within 4 h, compared to 15 cm in clayey soils over 8 h. Furthermore, sandy soils required less liquid nitrogen to achieve the same frozen column compared to clay soils, owing to their higher thermal conductivity and lower water retention. These findings highlight the superior efficiency of AGF in sandy soils under controlled conditions, particularly when water seepage is absent, and underscore the importance of optimizing compaction levels and freeze-thaw parameters to enhance the cost-effectiveness of soil stabilization. The study provides valuable insights into soil behavior during AGF, particularly the impact of thawing, supporting its broader application in various geotechnical projects.

The construction of diaphragm wall panels inevitably changes the initial stress condition and causes movements in the surrounding soil mass, which may also cause settlement and damages to adjacent buildings. Majority of current design and analyses of deep excavations assume that the diaphragm wall is wished-in-place, largely because of the complexities involved to consider the detailed wall installation process. Limited studies suggested that neglecting the wall installation effects would reduce the reliability of these analyses for both predictions and validations. This paper analyzes measured ground response and building settlements caused by diaphragm wall panel installation and highlights the importance of considering these installation effects in practical design. A realistic modeling procedure is then developed to incorporate the sequential diaphragm wall panel construction process in braced excavation analyses, to investigate the installation effects on adjacent ground and buildings. The computed results are consistent with those field measurements from different case studies. The benefits of the proposed approach are demonstrated though comparison with the conventional wished-in-place approach in the braced excavation analyses.

This study presents the design and structural analysis of a bridge to protect two natural gas pipelines against static and dynamic loads resulting from a new railway line to be constructed above them. Structural analyses were conducted considering earthquake effects, particularly using the load combinations and coefficients recommended by AASHTO LRFD [2017]. The railway bridge is not designed to span any crossings. However, since the existing railroad is situated directly on the ground, a train load is transferred to the pipelines through the ground. To reduce this load transfer, a 25-30cm gap is maintained between the deck and the ground in this protective bridge design proposal. The maximum anticipated displacement of the bridge was considered in the analysis. Site-Specific Earthquake Hazard Analysis was first performed for the proposed bridge due to the critical implications of the pipelines. In the second stage, the structure underwent nonlinear dynamic displacement loading and bridge-pile-soil interaction was analyzed using both linear and nonlinear methods. The performance targets - Uninterrupted Use for DD2a class ground motion and Controlled Damage for DD1 earthquake) - stipulated by the Turkish Bridge Design Standards [TBDS, 2020] were evaluated using strength-based linear and strain-based nonlinear analyses. The results confirmed that the proposed bridge satisfied all target safety levels. In conclusion, this study aims to guide both designers and practitioners, as it is among the first to address the newly enacted TBDS-2020 regulation in Turkiye and serves as an exemplary engineering solution for similar protective bridge designs.

Stress-induced anisotropy, the directional variation in soil properties under applied loads, significantly influences the soil behavior and stability of geotechnical structures. This review critically examines its impact on shear strength, pore pressure, stiffness, and stress-strain behavior of soils, offering insights into its fundamental mechanisms. Advancements in experimental methods, including bender element tests, true-triaxial testing, and hollow cylinder apparatus, are critically analyzed alongside analytical and numerical models that capture complex anisotropic responses under varied loading conditions. The study highlights the practical significance of incorporating the anisotropic behavior of soils in geotechnical design. From the literature, it can be concluded that neglecting stress-induced anisotropy can overestimate the factor of safety (FOS) of slopes up to 33% and underestimate displacements of foundations by 25-40%, leading to critical inaccuracies in the design. A case study of slope failure under anisotropic stress highlights the necessity of accounting for these effects. Challenges such as replicating realistic stress paths in laboratory tests and integrating anisotropic parameters in numerical frameworks are identified. Future directions include developing predictive models, automating analysis using machine learning, and validating findings through large-scale field studies. This review bridges theoretical advancements with practical applications, advocating for integrating stress-induced anisotropy, wherever applicable, into geotechnical practice to enhance infrastructure safety and resilience.

The soil behavior is rate-dependent as observed in the laboratory and field tests, and the undrained shear strength of clay is shown to increase with the strain rate in different shear modes. In practical situations, the foundations can be loaded at various time and rate scales, which will result in a wide range of magnitudes and inhomogeneous distribution of strain rates in the surrounding soil. This may cause difficulties in calculating the undrained bearing capacity of clay using the undrained shear strength from standard laboratory and field tests at a reference strain rate. In addition, the rate-dependent soil behavior will also affect the interpretation of in situ tests conducted at different loading rates (e.g., CPT, T-Bar, and pressuremeter tests) using procedures based on rate-independent soil models. This paper investigates the effect of loading rate on the undrained bearing capacity of clay using finite element analyses and a rate-dependent constitutive model, the MIT-SR, based on two classical problems in soil mechanics (i.e., the deeply-embedded rigid pile/pipe section, and the rigid strip footing). Computed results suggest that the undrained bearing capacity of clay is strongly affected by the loading rate of foundations, which is consistent with the model and field tests. It also highlights the difficulty to select appropriate undrained shear strength used for practical design, and the uncertainty to interpret field tests using bearing capacity factors derived from analytical solutions.

A method directly using rainfall records to predict a slope's potential instability is devised. The method consists of three sequential steps: identifying the critical suction stress (pore water pressure when soil is saturated) profile of a given slope, developing a rainfall intensity-duration threshold curve for the slope, and using rainfall record to determine if the threshold is reached (failure occurs) or not (no failure). It innovatively uses a slope's strength parameters and slope angle to develop the critical suction stress (tensile) or compressive pore water pressure profile where, at each depth within the slope, the effective stress reaches the failure state. Hydromechanical numerical modeling is then conducted under various rainfall intensities to identify their corresponding duration for slope failure, thus, the rainfall intensity-duration threshold curve of the slope. Two previously well-documented and studied rainfall-induced slope instability cases; one near the town of Edmonds, Washington State, and the other near the village of R & uuml;dlingen in northern Switzerland are used to validate the method. Excellent predictions of the slope failure depth and timing are demonstrated, indicating the effectiveness of the proposed method. Because the suction stress-based rainfall intensity-duration curve is characteristic of a given slope and it can be determined a priori, the method provides a practical way to conduct real-time rainfall monitoring and predict instability for a specific slope, and a pathway to forecast instability of natural slopes in a region.

This study presents a simple, yet robust testing methodology employed for investigating the mechanical behaviour of soils under cyclic loading conditions. Small cylindrical specimens of soil (10.5 mm diameter and 35.0 mm high) were subjected to oscillatory torsional loading in either strain sweep or stress sweep mode using the dynamic shear rheometer. Key mechanical properties, including dynamic shear modulus, phase angle, and energy dissipation capacity, were obtained and used to effectively identify threshold strain levels which differentiated the linear, nonlinear, and damage response of the soil. This study further applied the proposed method to stabilized soils to evaluate the effects of stabilizers on improving soil stiffness, while also considering their potential effects on increasing soil brittleness, which could ultimately lead to reduced resistance to fatigue cracking. The successful development of this testing protocol has the potential to evolve into a specification-type method due to its efficiency, repeatability, sensitivity, and fundamental robustness.

Earth construction is a sustainable and environmentally friendly approach to building. In addition to their good thermal performance, earth materials are abundant, inexpensive, and readily available, reducing the need for resource -intensive materials like concrete and steel. Regarding the construction process of earth structures, which is based on compaction, there is often a difference between the laboratory compaction process and the onsite one. The energy consumed onsite to produce earth structures is still approximative and uncontrolled, which affects considerably the mechanical performances of earth walls. Then, the investigation of the optimal compaction energy is necessary. To optimize the on -site compaction energy used in rammed earth (RE), an experimental study is carried out to compare the dynamic compaction usually applied to produce RE walls to the static compaction using a mechanical press. By considering increasing dynamic and static energies, the physical and mechanical properties are analyzed for each case. The obtained results show that RE walls can be replaced by prefabricated pressed earth blocks where the compaction energy is reduced by 60% and the compressive strength is enhanced by 70% using static compaction, thus achieving 4 MPa without stabilization. This solution allows to reduce the execution time and to control the quality of earth buildings.

An increase in the temperature of permafrost that is caused by global warming can lead to a significant decrease in shear strength. Seasonal freeze-thaw (F-T) cycles can also adversely affect the shear strength of soils. This can result in damages to infrastructure, negative impacts on the economy, and a decline in the quality of life. Thus, it is crucial to understand the shear strength of permafrost and seasonally frozen-thawed soils. Several studies have utilized various instruments to observe the behavior of soils under such conditions, including a temperature-controlled triaxial system to apply F-T cycles or a traditional direct shear apparatus placed within a temperature-controlled room. Since most commercial geotechnical labs do not have a temperature-controlled room or a temperature-controlled triaxial system, this article presents the design of a new cost-effective direct shear box that was developed to allow temperature-controlled testing in a traditional direct shear device. The modifications to the direct shear box comply with ASTM D3080/3080M, Standard Test Method for Direct Shear Test of Soils under Consolidated Drained Conditions. Like the standard direct shear box, it consists of two halves and a direct shear cap, but each of these components is hollow to allow for the circulation of glycol. The chiller is capable of imposing temperatures within the range of -40 degrees C to +40 degrees C on the sample being tested. It is also possible to freeze and thaw specimens at a desired normal stress while monitoring the associated heave and compression. The freezing mechanism applied to the soil sample affects the distribution of ice within the pore spaces, necessitating that samples be frozen from all sides if a uniform distribution of ice is necessary. Shear strength parameters from the newly designed temperature-controlled direct shear box matched well with those from the traditional shear box. In addition, the feasibility of temperature-controlled direct shear testing was evaluated at different temperatures, strain rates, and normal stresses.