Guan Rong

Previous freeze–thaw studies have mainly used uniaxial tests, leaving the effects of freeze–thaw damage and confinement on basalt behavior and physically interpretable triaxial strength estimation insufficiently resolved. Here, saturated basalt specimens subjected to 0, 10, 20, and 30 freeze–thaw cycles were tested under confining pressures of 0–40 MPa using a triaxial compression system. Stress–strain responses, failure modes, deviatoric stress strength, and Mohr–Coulomb parameters were analyzed; planar, binary quadratic, and freeze–thaw-dependent Mohr–Coulomb models were developed and compared. Freeze–thaw cycling intensified initial compaction and post-peak softening, whereas confinement shifted failure from axial splitting to shear-dominated or mixed modes. After 30 cycles, deviatoric stress strength decreased by 53.6% under uniaxial loading and by 41.1% at 40 MPa confinement; cohesion decreased by 46.2%, from 39.6 to 21.3 MPa, and the internal friction angle decreased from 30.84° to 27.04°. The Mohr–Coulomb model achieved a maximum absolute error of 10.2 MPa, a mean absolute error of 4.7 MPa, and a root-mean-square error of 5.6 MPa. Within 0–30 cycles and 0–40 MPa confinement, the model provides strength estimates for parameter selection and stability assessment of basalt engineering structures in cold regions.

Valley contraction poses a significant threat to high-arch dams, making the prediction of valley deformation a critical task in assessing the long-term performance of dams. The Baihetan dam is currently undergoing compression due to valley contraction, and its complex control mechanisms present major challenges in predicting valley deformation. This paper proposes a hybrid model to predict valley deformation in Baihetan, which integrates numerical simulation and statistical analysis to identify the main causes of river valley deformation and make predictions based on extrapolation. A transient numerical seepage model has been used to comprehensively characterize the complex seepage field in the Baihetan dam site area over nearly a decade following impoundment. The hybrid model was developed based on this foundation to determine the contribution of each factor using monitoring data. The model can then be used for time series extrapolation to predict long-term deformation. By June 2028, the valley near the dam is projected to experience a deformation rate of less than 1 mm per month, with a maximum contraction of approximately 26.7 mm. This study provides a basis for assessing the long-term operational safety of the Baihetan and offers valuable reference for similar studies on valley deformation.