An integrated constitutive model has been developed for rock-like materials, incorporating confinement-sensitive damage and bi-mechanism plasticity. The model aims to improve the capability of the conventional damage model in depicting the strengthening and brittle-to-ductile transitions that occur under both active and passive confinement conditions. A thermodynamic analysis of energy transformation and dissipation, considering both damage and plasticity, underpins the model's development. The model, rooted in damage-plastic theory, has been divided into two sub-models: (1) Confinement-Sensitive Model: This sub-model addresses the strengthening and ductility enhancements due to active confinement stress. It effectively captures the mechanical responses of rock-like materials under various levels of active confining stresses. (2) Endochronic Dilatancy Model: Based on endochronic theory, a separate dilatancy strain model is proposed, which effectively facilitates the interplay between lateral dilatancy and the growth of passive confining stress. Both sub-models, as well as the integrated model, have undergone validation using experimental data, including uniaxial tests, cyclic loading tests, actively confined tests, and passively confined tests of rock-like materials. These validations confirm the model's accuracy and reliability in predicting the mechanical behavior of rock-like materials under complex loading conditions.

Damping plays a crucial role in the design of offshore wind turbine (OWT) monopile foundations. The soil damping of the monopile-soil system (MSS) represents the energy dissipation mechanism arising from the interaction between the pile and the soil. It is typically derived by back-calculating from the overall damping measured in the entire OWT structure. However, few studies have independently examined the soil damping in MSS, and the impact of key parameters such as pile diameter, pile embedded depth, cyclic load amplitude, and load eccentricity on the variation of soil damping in MSS remains unclear. This paper introduces an elastoplastic-damage constitutive model for the numerical simulation of the damping ratio variation in seabed soil and MSS. The model is implemented in ABAQUS software and validated against cyclic triaxial tests on stiff clay soil. On this basis, a three-dimensional finite element sensitivity study was conducted to elucidate the effect of these key parameters on the MSS damping ratio. The results of the study reveal that the MSS damping ratio exhibits a nonlinear and asymmetric trend as the loading cycles increase. The MSS damping ratio decreases with increasing pile diameter and embedded depth but increases with increasing lateral cyclic load amplitude and load eccentricity from the mudline.

The study of the compression characteristics of loess in seasonal regions involves analyzing the mechanical properties and mesoscale damage evolution of intact loess subjected to dry-wet freeze-thaw cycles. This study meticulously examines the evolution of the stress-strain curve at the macroscale and the pore structure at the mesoscale of loess by consolidation and drainage triaxial shear tests, as well as nuclear magnetic resonance (NMR), under varying numbers of dry-wet freeze-thaw cycles. Then, utilizing the Duncan-Chang model (D-C), the damage model for intact loess is derived based on the principles of equivalent strain and Weibull distribution, with testing to verify its applicability. The results indicate that the stress-strain curve of undisturbed loess exhibits significant strain softening during the initial stage of the freeze-thaw dry-wet cycle. As the number of cycles increases, the degree of strain softening weakens and gradually exhibits a strain-hardening morphology; the volume strain also changes from dilatancy to shear contraction. According to the internal pore test data analysis, the undisturbed loess contributes two components to shear strength: cementation and friction during the shear process. The cementation component of the aggregate is destroyed after stress application, resulting in a gradual enlargement of the pore area, evidenced by the change from tiny pores into larger- and medium-sized pores. After 10 cycles, the internal pore area of the sample expands by nearly 35%, indicating that the localized damage caused by the dry-wet freeze-thaw cycle controls the macroscopic mechanical properties. Finally, a damage constitutive model is developed based on the experimental phenomena and mechanism analysis, and the model's validity is verified by comparing the experimental data with theoretical predictions.

This study investigated the small-strain dynamic properties of expanded polystyrene (EPS) lightweight soil (ELS), a low-density geosynthetic material used to stabilize slopes and alleviate the subgrade settlement of soft soil. Resonant column tests were conducted to evaluate the effects of EPS's granule content (20-60%), confining pressures (50 kPa, 100 kPa, and 200 kPa), and curing ages (3 days, 7 days, and 28 days) on the dynamic shear modulus (G) of ELS within a small strain range (10-6-10-4). The results indicate that ELS exhibits a high dynamic shear modulus under small strains, which increases with higher confining pressure and longer curing age but decreases with an increasing EPS granule content and dynamic shear strain, leading to mechanical property deterioration and structural degradation. The maximum shear modulus (Gmax) ranges from 64 MPa to 280 MPa, with a 60% reduction in Gmax observed as the EPS granule content increases and increases by 11% and 55% with higher confining pressure and longer curing ages, respectively. A damage model incorporating the EPS granule content (aE) and confining pressure (P) was established, effectively describing the attenuation behavior of G in ELS under small strains with higher accuracy than the Hardin-Drnevich model. This study also developed an engineering testing experiment that integrates materials science, soil mechanics, and environmental protection principles, enhancing students' interdisciplinary knowledge, innovation, and practical skills with implications for engineering construction, environmental protection, and experimental education.

Masonry walls represent a significant architectural heritage that continues to be prevalent in various regions. Ancient masonry walls are typically constructed using mortar composed of soil and water and are characterised by low adhesion. Presently, research on the factors affecting the stability of low-bond stone masonry walls is still in the preliminary stage and lacks a unified understanding. This study investigates the factors influencing the stability of low-bond stone masonry walls, focusing on the Royal City platform wall at Shimao Site in China. A scaled-down model was constructed based on the actual conditions of the Royal City platform wall, and Schneebeli rods were loaded into the experimental model. This study examines the effects of height-to-width ratio, retaining wall inclination angle, masonry method, and mortar joint strength on wall stability. The results indicate that as the height-to-width ratio and inclination angle of the retaining wall increase, its stability decreases, and the angle between the failure surface and the horizontal direction increases. While the masonry method has a relatively minor influence on wall stability, variations in the mortar joint strength significantly impact the stability of the retaining wall. Based on the experimental results, which revealed two failure modes of overturning and sliding, a stability calculation method for low-bond stone masonry walls was derived using the limit equilibrium method. The proposed method was applied to analyse the Royal City platform wall. The findings provide valuable insights into the restoration and preservation of low-bond stone masonry walls.

Localized rock failures, like cracks or shear bands, demand specific attention in modeling for solids and structures. This is due to the uncertainty of conventional continuum-based mechanical models when localized inelastic deformation has emerged. In such scenarios, as macroscopic inelastic reactions are primarily influenced by deformation and microstructural alterations within the localized area, internal variables that signify these microstructural changes should be established within this zone. Thus, localized deformation characteristics of rocks are studied here by the preset angle shear experiment. A method based on shear displacement and shear stress differences is proposed to identify the compaction, yielding, and residual points for enhancing the model's effectiveness and minimizing subjective influences. Next, a mechanical model for the localized shear band is depicted as an elasto-plastic model outlining the stress-displacement relation across both sides of the shear band. Incorporating damage theory and an elasto-plastic model, a proposed damage model is introduced to replicate shear stressdisplacement responses and localized damage evolution in intact rocks experiencing shear failure. Subsequently, a novel nonlinear mathematical model based on modified logistic growth theory is proposed for depicting the shear band's damage evolution pattern. Thereafter, an innovative damage model is proposed to effectively encompass diverse rock material behaviors, including elasticity, plasticity, and softening behaviors. Ultimately, the effects of the preset angles, temperature, normal stresses and the residual shear strength are carefully discussed. This discovery enhances rock research in the proposed damage model, particularly regarding shear failure mode. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/

Predisintegrated carbonaceous mudstone (PCM) that exhibits low strength and continuous disintegration is prone to wetting deformation after repeated seasonal rainfall. A reasonable assessment of wetting deformation is required to facilitate the settlement control of the PCM embankment when exposed to repeated rainfall. Herein, to reveal the wetting deformation mechanism of the PCM subjected to drying-wetting cycles, the effects of drying-wetting cycles on the wetting deformation characteristics of the PCM are investigated using the double-line method. Microscopic pore characteristics of the PCM under different drying-wetting cycles were analyzed through scanning electron microscope (SEM) micrographs. Comparative analysis of the wetting deformation data between the tests and the constitutive model considering the damage of drying-wetting cycles was carried out. The results showed that the deviator stress-strain relationship curves of the PCM exhibit the strain hardening without obvious peak and no strain softening phenomena. The critical wetting strain of the PCM was positively correlated with the number of drying-wetting cycles, while the critical deviator stress decreased with an increase in the number of drying-wetting cycles. As the number of cycles increased, the gelling material between the particles dissolved, the volume of pores inside the PCM increased, and the number of pores inside the PCM decreased. The porosity of PCM had a significant quadratic function with the number of drying-wetting cycles. A wetting deformation damage model was developed to calculate the wetting deformation of the PCM by considering the effects of drying-wetting cycles, which can be useful for evaluating rainfall-induced settlements of relevant engineering structures made from PCM.

The thermal effect has a significant impact on the activation and slip characteristics of fractures. In this study, four pairs of granite fractures were treated by temperatures T ranging from 25 degrees C to 900 degrees C. The fractures were then employed to carry out triaxial unloading-induced shear slip experiments. The step unloading of confining pressure s3 was used as a disturbed stress to activate fractures that were in a near-critical stress state. The slip characteristics, frictional behaviors, as well as damage modes of fractures with different T, were systematically investigated. The results show that at T = 25 degrees C and 300 degrees C, no stick-slip events were observed, and the slipping process of the fractures was characterized by aseismic slip and creep, respectively. For T = 600 degrees C and 900 degrees C, the fractures slipped stably, with occasional interruptions by episodic stick-slip events. Ultimately, they entered the dynamic slip stage after a series of consecutive stick-slip episodes. With increasing T, the number of sheared-off asperities increases due to thermal damage, which in turn leads to an increase in the occurrence of stick-slip events. The slip modes of the fractures transited from friction strengthening to friction weakening. As T increased from 300 degrees C to 900 degrees C, a considerable quantity of generated gouge layer acted as a lubricant for the slipping of fractures. This resulted in a notable increase in the proportion of aseismic slip, which rose from 24% to 54%. As the temperature increased from 25 degrees C to 900 degrees C, the crack length increased exponentially from 2.975 mm to 45.349 mm. For T = 600 degrees C and 900 degrees C, the duration between stick-slip events decreased as stick-slip events occurred more frequently. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published 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/).

Deep rocks encountered in underground engineering are frequently in complex in situ environments and experience both excavation disturbance during construction and cyclic loading throughout the long-term operation. Understanding the fatigue behavior of excavation-disturbed rocks in complex stress environments is critical for assessing the long-term stability of deep rock structures. Hence, an experimental method has been developed to capture the fatigue damage process of rocks while considering the in situ environment and excavation disturbance. Using this method, a series of triaxial fatigue damage experiments were conducted on Jinping deep marble samples from various in situ environments of 100 m, 1000 m, 1800 m, and 2400 m to better understand the variation in fatigue characteristics at different depths. With increasing depth, the samples experienced more cycles and greater fatigue deformation before failure. Further insights were gained into the fatigue damage behavior in terms of stiffness degradation, energy dissipation and irreversible strain accumulation. A decrease in the elastic modulus and an increase in the dissipated energy and irreversible strain exhibit an evolution pattern of initial/stabilization/acceleration, reflecting the nonlinear fatigue process that occurs inside marble. With increasing depth, marble samples have longer fatigue lives but exhibit more significant stiffness loss, energy dissipation and irrecoverable deformation accumulation; thus, evaluating the instability of deep rock structures solely using fatigue life alone is inadequate. Moreover, the previously reported inverted Sshaped evolution of fatigue damage was observed, and it was found that an increase in depth leads to an earlier onset of the accelerated fatigue damage stage with greater dominance of fatigue failure. Based on the nonlinear strain, loading cycle variable and fatigue life, a highly accurate nonlinear fatigue model was developed to describe the complete inverted S-shaped evolution pattern of fatigue damage, which demonstrated excellent practical implications for the theoretical characterization of anisotropic fatigue damage in disturbed Jinping marble. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published 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/).

For a binary structure slope with a soil layer on the top and a rock layer on the bottom, during the rainfall process, surface runoff will cause soil and water loss on the slope surface and damage to the slope environment. When rainwater infiltrates into the slope, the pore water pressure in the soil gradually increases, the shear strength of the soil decreases, and a weak zone is formed at the soil-rock interface, which has a significant impact on the stability of the slope. Therefore, to study the soil and water loss on the slope surface and the stability of the slope under rainfall conditions, we used theoretical analysis, indoor model tests, and numerical simulations to conduct a comprehensive exploration of this issue, and the following conclusions were formed: the pore water pressure in the shallow layer is greater than that in the deep layer, and the pore water pressure at the toe of the slope is greater than that at the top of the slope; as the slope gradient increases, the time when the pore water pressure at the toe of the slope begins to respond gradually speeds up; the slope displacement first occurs at the lower part of the slope, then in the middle, and finally at the upper part; the time when the displacement at each point on the slope surface begins to respond gradually speeds up with the increase in the slope; the damage form at a small slope gradient is mainly flow sliding, and the damage process is continuous; the damage form at a large slope gradient is mainly flow sliding and overall sliding, and the damage process is continuous and sudden; when the binary structure slope fails, the sliding surface includes the internal sliding surface of the soil and the sliding surface at the soil-rock interface, but when the slope gradient is small, the relative sliding at the soil-rock interface is small, and a continuous sliding surface cannot be formed; and when the slope gradients are small (30 degrees and 40 degrees), the displacement decreases continuously from top to bottom, and no overall sliding surface is formed. The larger values of plastic strain mainly occur in the upper and middle parts of the slope, there is no formation of a continuous plastic strain zone, and the damage mode is flow sliding; when the slope gradients are large (50 degrees and 60 degrees), the displacement is the largest in the upper part, and a large displacement also occurs in the lower part, forming a sliding surface that penetrates through the soil-soil and rock-soil layers. The larger values of plastic strain occur in the upper, middle, and lower parts of the slope, a continuous plastic strain zone is formed, and the damage modes are flow sliding and overall sliding; numerical simulations were carried out on a typical actual slope, and consistent results were obtained.