Cemented sandy gravel is often used to enhance the foundation soil of engineering projects. This paper presents results of triaxial tests on cemented sandy gravel specimens. We compared 8 cemented specimens and 4 uncemented specimens. The strength, dilatancy, and stiffness behavior of both cemented and uncemented specimens are compared. The strength of cemented specimens is significantly greater than that of uncemented specimens, and the cemented specimens demonstrate pronounced expansion characteristics. The peak friction angle of the cemented specimen shows a linear relationship with the confining pressure: psi = 68.1-18.2lg(sigma 3/pa). To quantify the structural strength of the cemented specimens, a structural damage parameter is introduced based on the differences in mechanical properties between the two materials. The structural damage parameter first increases and then decreases as shearing progresses, and a hump curve function is used to describe this behavior. In the frame of the generalized plasticity, a novel elastoplastic model is established, considering the structural parameter as a factor of the plastic modulus, loading vectors and plastic flow direction vectors. The calculated values fit well with the experimental results. The model can reflect the characteristics of cemented sandy gravel, in terms of stress softening, residual strength, and volumetric dilation. Finally, the model is used to evaluate the deformation of a sluice dam foundation after being enhanced with cemented sandy gravel. The results show that after treatment, both the settlement of the gate floor and the shear deformation of the waterstops can be reduced by more than 10%.

This study investigates the mechanical behavior of gravelly soil under various confining pressures using large-size triaxial cyclic tests and a novel constitutive model. Key properties analyzed include stress-dependent dilatation, nonlinear strength, cumulative plastic strain, cyclic hysteresis, hardening, and particle breakage. Experimental results show that confining pressure significantly affects volume deformation, strength, and failure modes. Specifically, volume deformation shifts from dilatation to contraction with increasing pressure, and failure modes transition from drum-shaped to compressive shear. The developed model integrates stress-dilatancy equations, plastic flow directions, and plastic moduli within the critical state soil mechanics framework, effectively capturing cyclic loading and unloading behaviors. A particle breakage index and a differential equation for void ratio evolution are included to reflect relative density changes. The material constants of this constitutive model are derived from large-size triaxial cyclic tests. The model's material constants are derived from large-size triaxial cyclic tests. Comparison with experimental data confirms the model's accuracy and potential applications in stress path analysis and complex engineering projects, demonstrating its adaptability to varying mechanical stress conditions.

Nowadays, with the widespread supply of very powerful laboratory and computer equipment, it is expected that the analyses conducted for geotechnical problems are carried out with very high precision. Precise analyses lead to better knowledge of structures' behavior, which, in turn, reduces the costs related to uncertainty of materials' behavior. A precise analysis necessitates a precise knowledge and definition of the behavior of the constituent materials, which itself requires applying an appropriate constitutive model to show the behavior of materials. Constitutive models used in the generalized plasticity framework are very powerful constitutive models for the simulation of sand behavior. However, the simulation of a cyclic behavior in these models, especially the simulation of the undrained cyclic behavior, is not well-recognized. In this study, in order to eliminate the weakness of generalized constitutive models under cyclic loading, a new equation is presented to substitute the so-called coefficient of the discrete memory factor to consider the loading history in such a way that the plastic modulus is modified during reloading and, as a result, more appropriate predictions of sand behavior are obtained. The performance accuracy of the proposed coefficient was evaluated in accordance with the experimental data. Finally, the results show that after using the modification of the loading history coefficient, predictions of the constitutive model are significantly improved.

In this study, constitutive behavior of granular soils is modeled through a generalized plasticity-based theoretical framework. The soil hardening is addressed by a novel relationship proposed to calculate plastic strains and their evolution during loading history. The model is effective in predicting the response and incorporating it into a numerical scheme. Focus is given to stress ratios yielding liquefaction in a few stress cycles. The proposed hardening law is based upon a combined deviatoric-volumetric hardening rule updating the stress-strain relationship and plastic strain vector. Numerous undrained monotonic and cyclic triaxial tests are simulated for verification of the constitutive formulation. Results indicate that the developed model for sand-like cohesionless soils proves to match fairly well with the available experimental data. Plastic strains are calculated accurately and accumulated pore pressures are well captured. Triaxial test simulations exhibit a successfully improved way of capturing the essential static and cyclic behavior of granular soils.