Yalin Yu

The construction of high dams and large hydropower projects significantly alters the hydrodynamic environment of reservoir shorelines, inducing periodic water level fluctuations. These fluctuations trigger complex hydro-mechanical interactions within the surrounding rock mass, leading to the development of transient seepage fields, cyclic changes in pore water pressure, and progressive degradation of rock structure. Consequently, the risk of slope failures in hydro-fluctuation belts is substantially increased. In this study, a typical anti-dip rock slope near Huangdeng hydropower station was selected to study the fluid–solid coupling mechanism of slope instability under hydro-fluctuation belt. A series of physical model tests were conducted under controlled hydrodynamic conditions to simulate the weakening of rock mass due to seepage. The coupled evolution of displacement and strain was recorded throughout the failure process. The primary findings of this research are as follows: The toppling failure process of the anti-dip rock slope model near the reservoir bank can be categorized into six distinct stages: compaction, creep, crack initiation, crack propagation, crack penetration, and instability failure. Under hydro-fluctuation belt rock mass degradation, the reservoir bank slope model exhibited increased crack generation, with the displacement field, strain field, and Newton forces all reaching critical warning thresholds, ultimately leading to large-scale slope instability. The results demonstrated that displacement changes lagged behind Newton force variations by 90–100 s, confirming that Newton force monitoring represents an effective approach for pre-sliding landslide warning.

The construction of the cross passage changes the main tunnels segment from a complete cylindrical structure to a notched unstable stressed structure. Thus, the overall force (bending and shearing) performance of the main tunnels is considerably decreased. The excavation of the cross passage also destroys the stability of the original soil layer and main tunnels and causes difficulty in avoiding the settlement of the surface and main tunnels. Numerical simulation analysis of the mechanical characteristics and influencing factors analysis were carried out using FLAC3D. Results show that (1) the construction of the cross passage largely disturbs the main tunnels. The settlement of the intersection part of the main tunnels and cross passage is mainly concentrated from −7 m to 7 m. (2) During the construction of the cross passage, the original main tunnels are subjected to stress redistribution, which causes stress concentration in the intersecting segments, especially in the opening side segment has an unfavorable force form in which the upper and lower sections are integrally pulled. (3) The construction of the cross passage causes a large tensile stress area in the structure as well. As a result, the overall tension of the upper and lower sections of the structure and the compression of the hance are unfavorable. (4) The influence of the excavation of the cross passage on the surface and main tunnels is related to the buried depth, intersection angle, excavation method, and grouting range. Therefore, the influence of different parameters can be analyzed by changing the model parameters.