Akademik Veri Yönetim Sistemi
4th Global Conference on Engineering Research (GLOBCER'24), Balıkesir, Türkiye, 16 - 19 Ekim 2024, ss.239
ABSTRACT
Soil deformation characteristics are influenced by factors such as effective stress, relative density, strain level, and stress-strain history. The mechanical behavior of cohesionless soil, including stress-strain and dilatancy responses, is notably affected by changes in confining pressure. Soil behavior is inherently non-linear, meaning soil stiffness varies with the stress levels within the soil mass. In the Hardening Soil (HS) model, soil behavior is represented more accurately by incorporating three distinct soil stiffness moduli. This model also considers the stress dependence of soil stiffness and the dilatancy behavior specific to sand. Additionally, the yield surface in the HS model can expand as plastic strains accumulate. Advanced models like the HS model can also account for loading history through parameters such as the overconsolidation ratio (OCR) or pre-overburden pressure (POP). The stiffness parameters 𝐸𝐸50ref, 𝐸𝐸urref, and 𝐸𝐸oedref correspond to reference pressures and are crucial for modeling soil behavior. Specifically, 𝐸𝐸50ref (secant modulus) is used to represent the soil's response to plastic deformations during primary deviatoric loading. In contrast, 𝐸𝐸urref (unloading-reloading modulus) characterizes the soil's elastic behavior during unloading and reloading phases; this parameter can often be calculated using a specific equation. The reference value 𝐸𝐸oedref (odeometric modulus) is commonly used in soil mechanics to represent the modulus of elasticity from oedometer tests. In instances where direct measurement of 𝐸𝐸50 or 𝐸𝐸ur from experimental data is not feasible, it is often beneficial to employ the approximation 𝐸𝐸urref / 𝐸𝐸50ref = 2.00 to 6.00, with a commonly accepted mean value of 3.00. This stiffness modulus ratio serves as a comparative metric, effectively characterizing the stiffness behavior of soil under varying loading conditions. This research employs finite element software to perform comprehensive numerical simulations. The study is structured into two principal phases: validation and soil analysis. During the validation phase, the full-scale loading tests executed by Briaud and Gibbens (1997) on square footings resting on sandy substrates have been meticulously replicated and assessed using finite element modeling (FEM). This methodology facilitates the development of a rigorously calibrated and validated finite element model, subsequently utilized for generating an extensive dataset. In this study, the effect of varying stiffness modulus ratios (𝐸𝐸urref / 𝐸𝐸50ref = 2.00, 3.00, 4.00, 5.00, 6.00, 7.00) on the load-bearing capacity of sand is examined through finite element analysis utilizing the HS method. The findings of this study indicate that the stiffness modulus ratio notably influences the load-bearing capacity of sand, with a pronounced effect observed between ratios of 2.00 and 3.00. Beyond this threshold, the tendency for diminishing returns in load-bearing capacity suggests the need to establish an optimal stiffness ratio for engineering applications that balances performance with material efficiency.
Keywords—Hardening Soil; Stiffness Modulus; Bearing Capacity; Finite Element