Coal gangue concrete (CGC) is an effective green building material that can promote the resource utilization of solid waste. To study its durability performance and degradation mechanism under sulfate attack with dry-wet cycles, and to realize the intelligent prediction of mechanical properties, this study prepared CGC specimens with a water-to-binder ratio of 0.4, a fine aggregate replacement rate of 20%, and coarse aggregate replacement rates of 0%, 20%, 50%, 80%, and 100%. The specimens were tested under 30, 60, 90, and 120 dry-wet cycles in 10% MgSO₄ solution. Mass loss, relative dynamic elastic modulus, and compressive and flexural strength corrosion resistance coefficients were used as evaluation indices, and SEM and XRD were adopted to analyze microstructural deterioration. A database compiled from literature data was established, and six machine learning models-random forest (RF), artificial neural network (ANN), decision tree (DT), support vector machine (SVM), particle swarm optimization-artificial neural network (PSO-ANN), and particle swarm optimization-support vector machine (PSO-SVM) were constructed to predict the strength corrosion resistance coefficients. Test results indicate that all macroscopic indices first increased and then decreased with the number of dry-wet cycles. Early ettringite and gypsum products filled internal pores, while prolonged sulfate attack caused decalcification and structural degradation of C-S-H gel, resulting in obvious performance loss. The PSO-SVM model showed the best prediction accuracy, with R² values of 0.912 and 0.981 for compressive and flexural strength corrosion resistance coefficients, respectively. Feature importance analysis shows that dry-wet cycles had the most significant negative impact, followed by the coal gangue fine aggregate replacement rate. This study provides support for the durability evaluation and intelligent prediction of coal gangue concrete in sulfate environments.

Foliated metamorphic rock exists widely in the surrounding rock of tunnel structures, underground utility caverns and mountain civil structures, and its laminated foliation structure induces obvious anisotropic time-dependent creep deformation, which seriously threatens the long-term service safety of underground building support systems. The strength and time-dependent deformation of foliated phyllite vary sharply with bedding dip angles, and long-term creep easily triggers large convergence, secondary-lining cracking and structural intrusion failure of tunnel structures. In this work, multi-stage uniaxial compression creep tests were carried out on sericite phyllite specimens with foliation dip angles of 0°, 30°, 45° and 90° using a programmable rock creep testing apparatus, aiming to investigate the anisotropic creep behaviors of phyllite surrounding rock for tunnel engineering. The anisotropic P-wave velocity characteristics of phyllite under different bedding angles were first analyzed to quantify the directional structural difference in the rock matrix. Based on the creep test curves, the full-stage deformation laws including instantaneous strain, decelerating creep, steady-state creep and accelerating creep were systematically summarized for specimens with different bedding orientations. Combined with macroscopic creep failure modes, phenomenological analysis was performed on the anisotropic creep damage behavior controlled by foliation weak planes. The results demonstrate that inclined bedding phyllite presents the most severe creep deformation and steady-state creep rate, and three typical creep failure modes (cross-bedding shear failure, tensile splitting failure, bedding slip shear failure) correspond to horizontal, vertical and inclined foliation specimens respectively. This study quantitatively reveals the time-dependent anisotropic mechanical properties of foliated soft rock, establishes a systematic experimental database and provides experimental basis for long-term stability prediction, and enriches the rheological research system for the durability evaluation of underground civil structures.