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Conference Open access Aug 2026

Mechanical properties and multi-factor ANOVA of reef limestone under cyclic loading after temperature-CO2 pressure dissolution

Reef limestone, as a crucial geological foundation for marine engineering, faces significant challenges regarding its long-term mechanical stability under complex marine environments. To address the coupled effects of chemical dissolution and periodic wave loading in deep-sea and island reef engineering, this study conducted cyclic loading tests on reef limestone with varying initial porosities after dissolution under different temperature and CO2 pressure conditions. Based on 18 groups of multi-factor orthogonal tests, the macroscopic stress-strain hysteresis characteristics were systematically analyzed, and an Analysis of Variance (ANOVA) was performed using the axial deformation increment as the damage evaluation index. The results indicate that the coupled dissolution of temperature and high-pressure CO2 significantly increases the porosity and weakens the internal cementation of the reef limestone, leading to a substantially accelerated accumulation rate of plastic strain and broader hysteresis loops under cyclic loading. ANOVA quantitatively reveals that at a 95% confidence level, dissolution temperature (P=0.0130), CO2 pressure (P=0.0389), stress amplitude (P=0.0356), and initial porosity (P=0.0395) exert a significant controlling effect on axial cumulative deformation. In contrast, the effect of loading frequency (within the 0.25∼0.5 Hz range, P=0.9605) is negligible, suggesting it can be reasonably simplified in practical low-frequency dynamic load designs. This study elucidates the coupled degradation mechanism of chemical dissolution and fatigue loading, providing essential mechanical parameters and a theoretical basis for evaluating the long-term stability and predicting the service life of deep marine foundations.

Zi-Heng Rao, Hong Zhang, Zhao Luo · 0 citations
Open access Aug 2026

Fracture evolution of micritic bioclastic limestone under Brazilian splitting: a comparison between natural and water-saturated states

The tensile strength properties and the initiation and propagation of tensile cracks within micritic bioclastic limestone–which forms the surrounding rock mass at the tunnel exit of the Altash Water Conservancy Project–pose a threat to engineering stability. To investigate the differences in tensile strength and stress-induced crack evolution under natural and water-saturated conditions, a comparative experimental study was conducted using Brazilian splitting tests coupled with acoustic emission (AE) monitoring. The results demonstrate that, compared with natural specimens, saturated limestone exhibits a 16.54% reduction in tensile strength. The failure process can be categorized into three distinct stages: compaction, quasi-linear elasticity, and unstable crack propagation. Furthermore, AE analysis indicates that while overall AE activity decreases following water saturation, the proportion of tensile cracks increases from 92.30% to 95.14%. Conversely, under natural conditions, shear cracks are more active and initiate earlier. Microscopically, the high content of bioclasts and associated complex interconnected pores (e.g., body cavity and secondary dissolution pores) endow the rock with remarkable hydrophilic and water-retention characteristics. Coupled with the presence of the abundant hydrophilic mineral illite, these factors collectively exacerbate water-rock interactions, driving the significant degradation of the rock’s mechanical properties from both material and structural perspectives.

Zuguo Mo, Maojun Huang, Yong Wu et al. · 0 citations
Open access Aug 2026

Mechanical Properties of Limestone Under Different Confining Pressures and Wet–Dry Cycles

During the operation of large reservoirs, slope rock masses at different elevations are subjected to confining pressure variation and alternating wet–dry cycles induced by water-level fluctuations, resulting in the evolution of their mechanical properties. To investigate this issue, conventional triaxial compression tests were conducted on limestone from Badong County in the Three Gorges Reservoir area under confining pressures of 5–20 MPa and 0–50 wet–dry cycles. The results show that confining pressure significantly enhances limestone strength, whereas wet–dry cycles induce a progressive deterioration in mechanical properties. Under the same confining pressure, the deterioration exhibits a staged characteristic, with a rapid decrease at the early stage followed by a slower decline. Higher confining pressure effectively suppresses crack propagation and mitigates the degradation caused by wet–dry cycling. Meanwhile, wet–dry cycles promote the transition of the failure mode from single-fracture failure to multi-fracture fragmentation. The elastic modulus, cohesion, and internal friction angle all decrease exponentially with increasing wet–dry cycles. Based on damage mechanics theory, a constitutive relationship considering wet–dry cycle effects was established to characterize rock stiffness degradation and its influence on the overall mechanical response. The proposed model effectively describes the evolution of mechanical parameters and deformation characteristics under wet–dry cycling conditions. This study provides an experimental and theoretical basis for evaluating the long-term stability of reservoir slopes.

Zongli Yang, Shaowu Zhou, Peng Lin et al. · 0 citations
Open access Aug 2026

Deterioration Mechanism and Constitutive Model of BFRC Corroded by Acid Rain

To elucidate the long-term degradation mechanism of basalt-fiber-reinforced concrete (BFRC) subjected to acid rain corrosion, this study conducted mechanical tests on BFRC specimens with a fiber content of 0.15% under simulated acid rain (pH = 3.0) over 0–120 corrosion cycles. Results reveal a nonlinear evolution in both compressive and splitting tensile strengths—an initial decrease, subsequent increase, and final gradual decline—with peak values attained at 60 and 30 cycles, respectively, corresponding to maximum enhancements of 20% and 45% relative to the initial strength. Microstructural analyses (SEM-EDS) identify a three-phase deterioration process: chemical dissolution (surface decalcification), competitive pore filling coupled with C-S-H decalcification, and expansive cracking induced by ettringite formation. Integrating the experimental data and degradation mechanisms with maturity theory, a dynamic constitutive model incorporating corrosion cycles is developed. The model accurately predicts the time-dependent mechanical degradation of BFRC under acid rain exposure, providing a theoretical foundation for durability design and assessment of fiber-reinforced concrete in corrosive environments.

Xinzhong Wang, Linshu Li, Mei Wei et al. · 0 citations
Open access Aug 2026

Moisture-induced degradation of clay-bearing sandstone

Clay-bearing sandstones used in the construction of historic monuments, churches, and castles are highly susceptible to contour scaling, which manifests as fractures parallel to the exposed facades. Repeated wetting–drying cycles accelerate material degradation through stiffness reduction and hygric deformation induced by swelling clays. This in turn alters the hygro-thermal (HT) properties of the stone. In this study, a scalar damage variable is employed within the framework of continuum damage mechanics to characterize the evolving damage state under the influence of moisture fields. The most critical climatic conditions that lead to degradation are first identified through hygro-thermal simulations. Subsequently, a fully coupled hygro-thermo-mechanical (HTM) model is developed to account for both moisture transport and material degradation. The results demonstrate that contour scaling can occur solely due to moisture cycling, even in the absence of freezing or salt crystallization effects. As such, subsurface zones of damage localization and a water-accumulation layer emerge that align well with on-site observations, pointing at potential damage mechanisms such as contour scaling.

You-yuan Wang, F. Wittel · 0 citations
Jul 2026

A thermo-mechanical constitutive model for fine-grained soils under cyclic and monotonic loading

Geothermal systems and geostructures, as sustainable energy sources, undergo daily and seasonal temperature fluctuations that significantly influence their mechanical response. Reliable prediction of thermally induced deformations therefore requires advanced thermo-mechanical constitutive models. Existing approaches often address constant elevated temperatures but fail to capture multiple thermal cycles or the coupled effect of mechanical cycling under heating. This study presents a hypoplastic thermo-mechanical model enhanced with the extended intergranular strain anisotropy concept to reproduce small-strain behaviour. Experimental evidence shows that normally consolidated fine-grained soils, when subjected to repeated thermal cycles, exhibit a transition to an overconsolidated state after the first heating–cooling cycle. To capture this, the model introduces a temperature-dependent preloading surface, enabling the evolution of the three-dimensional overconsolidation ratio under thermal cyclic loading. In addition, the original viscous strain-rate mechanism at ambient conditions is preserved, ensuring a consistent representation of rate effects under coupled thermal and mechanical actions. The proposed model is validated against diverse thermo-mechanical loading paths, including monotonic and cyclic scenarios, across different soil types. The results demonstrate its capability to capture key aspects of the complex response of fine-grained soils under combined thermal and mechanical loading, indicating its potential applicability to energy geotechnical problems.

M. Ashrafi, M. Tafili, T. Wichtmann · 0 citations