Cemented sand-gravel (CSG) is an innovative material for dam construction with a wide range of applications. Nevertheless, a comprehensive understanding of the dynamic properties of CSG is lacking. A series of cyclic triaxial dynamic shear tests were carried out on CSG materials to investigate their complex dynamic mechanical properties, leading to the establishment of a dynamic constitutive model considering damage. The findings indicate that both the application of confining pressure and the addition of cementitious material have a noticeable influence on the morphology of the hysteresis curve. Further research scrutiny reveals that augmenting confining pressure and gel content leads to an increase in the dynamic shear modulus and a decrease in damping ratio. Furthermore, a constitutive dynamic damage constitutive model was constructed by linking a damage element to the generalized Kelvin model and defining the damage variable D based on energy interaction principles. The theoretical formulas for dynamic shear modulus and damping ratio were adjusted accordingly. In addition, the stiffness matrix of the dynamic damage constitutive model was derived, which demonstrated its strong fitting effects in dynamic triaxial shear tests on CSG. Finally, the dynamic response and damage distribution in the dam body under dynamic loading were analyzed using a selected CSG dam in China.

The weakening of loess structure under hydro-mechanical effect is an important reason for collapsible deformation of loess. Therefore, when establishing the constitutive model of unsaturated loess, it is necessary to consider the influence of loess structure to truly reflect the mechanical characteristics. A modified elastoplastic damage structural constitutive model (MEDSCM) is proposed for unsaturated Q(3) undisturbed loess based on the modified Barcelona basic model (MBBM), assuming that the yield stress of undisturbed loess is a coupling of remolded loess and structure, and adopting the non-associated flow rule. The structural evolution equations of unsaturated Q(3) loess in loading and collapsing are introduced respectively, and obtained the constitutive model of soil skeleton in loading and collapsing. There are a total of 18 parameters for the loading model and 15 parameters for the collapsibility model, which are determined by mechanical tests on unsaturated loess. By comparing the triaxial compression and collapsible test data with the model calculation results, the accuracy of the model is verified, and progress has been made in describing the weak hardening characteristics of unsaturated loess. The research results provide a new attempt for further understanding the mechanical properties of loess.

The establishment of mechanical models of rocks can provide crucial guidance to the surrounding rocks stability analysis in the rock engineering. According to statistical damage theory and Mohr-Coulomb strength criterion, the Logistic model is used to yield the damage evolution equation and further establish statistical damage constitutive model for describing the whole failure process of rocks. Then, the rationality of the proposed damage model is proved by comparing with the different test curves, and damage evolution laws are summarized into four stages, including: slow-growth stage, rapid-growth stage, constant-speed-similar growth stage and speed-reducing growth stage. Physical meanings of model parameters r' and m are also discussed. Finally, to verify the application of this proposed model, this damage constitutive model is developed and implemented to simulate the tunnel excavation and analyze the stability of surrounding rocks by using Fortran, python and Abaqus. The displacement data on site is used to prove the superiority of proposed damage constitutive model compared with the existing ones in Abaqus. The research outcomes presented in this paper can also provide useful references for the theory and application of rock mechanics.

To elucidate the degradation mechanism of expansive soil-rubber fiber (ESR) under freeze-thaw cycles, freeze-thaw cycle tests and consolidated undrained tests were conducted on the saturated ESR. The study quantified the elastic modulus and damage variables of ESR under different numbers of freeze-thaw cycles and confining pressure, and proposed a damage constitutive model for ESR. The primary findings indicate that: (1) The effective stress paths of ESR exhibit similarity across different numbers of freeze-thaw cycles, the critical stress ratio slightly decreased by 8.8%, while the normalized elastic modulus experienced a significant reduction, dropping to 42.1%. (2) When considering the damage threshold, the shear process of ESR can be divided into three stages: weak damage, damage development, and failure. As strain increases, the microdefects of ESR gradually develop, penetrating macroscopic cracks and converging to form the main rupture surface. Eventually, the damage value reaches 1. (3) Due to the effect of freeze-thaw cycles, initial damage exists for ESR, which is positively correlated with the number of freeze-thaw cycles. The rubber fibers act as tensile elements, and the ESR damage evolution curves intersect one after another, showing obvious plastic characteristics in the late stage of shear. (4) Confining pressure plays a role in limiting the development of ESR microcracks. The damage deterioration of ESR decreases with an increase in confining pressure, leading to an increase in ESR strength. (5) Through a comparison of the test curve and the theoretical curve, this study validates the rationality of the damage constitutive model of ESR under established freeze-thaw cycles. Furthermore, it accurately describes the nonlinear impact of freeze-thaw cycles and confining pressure on the ESR total damage.

For reservoir landslide, in addition to hydrological conditions, creep properties of soils play an important role in explaining the mechanisms behind landslide movement. When studying the creep characteristics of geotechnical materials in reservoir area, most of them only consider the influence of a single factor (i.e. confining pressure, water content or osmotic pressure) on the creep behavior at present. In order to better describe the creep behavior of clay-gravel composite, this paper considers the effects of the initial water content and the saturation-undersaturation cycle together on the creep properties, and introduces the time-damage function to establish a novel creep-damage constitutive model. Compared with the classical Burgers model, this model can well characterize the creep experimental data with high accuracy, especially in the accelerated creep stage. Then, FLAC3D software is used as a platform to realize the proposed model applied to the long-term stability analysis of Woshaxi landslide by using C + + language. Comparing the Burgers model by the calculation, the proposed model shows a better reflection of the effect of initial water content and the number of saturation-undersaturation cycles on creep as well as being able to describe the accelerated creep phase. It is hoped that this research can provide scientific and engineering application value for the mitigation of the disasters on the reservoir bank slope.

This research develops an elastoplastic damage constitutive model incorporating the strain softening response of common engineering soil materials in southeastern Xizang to evaluate and optimize reinforcement solutions for highway-traversing landslide accumulations. Grounded in deterioration mechanics theory, the model characterizes the progressive strength loss and failure evolution of the soils. Verified and calibrated, it is numerically implemented in FLAC3D to simulate the stability conditions of a landslide affecting planned highway infrastructure in southeastern Xizang. Safety factors of 1.25, 1.07, and 1.02 under normal operation, rainfall, and seismic excitation loads, respectively, reveal the inadequacy of intrinsic stability. Consequently, dynamic compaction and chemical grouting techniques are assessed via simulation. An optimal strategy, entailing 6-m-deep densification at the highway location with 10% silica fume enhancement of 66.3% of the landslide area and 50.8% of the soil-bedrock interface, results in safety factors of 1.70, 1.49, and 1.23 for the three scenarios. The improved area is minimized to streamline construction practicality and economics while preserving geotechnical integrity. The integrated modeling outcomes demonstrate the model's capability in capturing localized incremental damage and the efficacy of numerical simulation for stability diagnosis and targeted remediation of intricate landslides. Advancements in constitutive relations development are vital for further innovation in geohazard evaluation and infrastructure safety assurance.

The study aimed to investigate the influence of dry-wet freeze-thaw cycles on the mechanical properties of undisturbed loess and evolution of microscopic damage. In order to analyse the stress-strain curves and chang law of strengch index and mesoscopic damage of pores from a macro and meso perspective, the research employed consolidation drainage triaxial shear tests (CD) and nuclear magnetic resonance tests under varying dry-wet freeze-thaw cycle durations. On this basis, the strength distribution of loess was assumed to follow a composite function, a statistical damage constitutive model of loess was established and its applicability was verified. The key findings and observations are summarized as follows. The stress-strain curve of the soil exhibited strain softening, with the degree of softening gradually decreasing with an increase in the number of cycles. The peak value of deviatoric stress decreased with the number of cycles and tended to be stable gradually, and the attenuation degree was most significant at the second cycle, decreasing by 17.6%, 23.2%, 24.5% and 18.1% respectively under different confining pressures. The circulation action led to damage to the cemented block in the soil, resulting in a gradual increase in internal pore area, primarily due to the transformation of small pores into large pores. With an increase in the number of cycles, the internal structure of the soil gradually became more stable.

The tensile -shear interactive damage (TSID) model is a novel and powerful constitutive model for rocklike materials. This study proposes a methodology to calibrate the TSID model parameters to simulate sandstone. The basic parameters of sandstone are determined through a series of static and dynamic tests, including uniaxial compression, Brazilian disc, triaxial compression under varying confining pressures, hydrostatic compression, and dynamic compression and tensile tests with a split Hopkinson pressure bar. Based on the sandstone test results from this study and previous research, a step-by-step procedure for parameter calibration is outlined, which accounts for the categories of the strength surface, equation of state (EOS), strain rate effect, and damage. The calibrated parameters are verified through numerical tests that correspond to the experimental loading conditions. Consistency between numerical results and experimental data indicates the precision and reliability of the calibrated parameters. The methodology presented in this study is scientifically sound, straightforward, and essential for improving the TSID model. Furthermore, it has the potential to contribute to other rock constitutive models, particularly new user -defined models. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).