坝基稳定是高拱坝安全的核心, 复杂坝基中软弱带的加固处理设计是高拱坝设计中的难点问题。提出了一种基于能量指标的坝基软弱带稳定评价和加固处理确定方法, 建立了基于能量耗散率及域内积分变化的稳定性演化分析模型, 基于软弱带的稳定性演化规律确定需要加固的关键软弱带及其加固部位。将该方法用于某高拱坝坝基平行断层组的稳定性分析和加固处理设计中。最后综合多项指标对确定的加固方案的效果进行了分析评价。结果表明, 坝肩断层在蓄水后能量耗散率及其域内积分呈现先迅速增大、后逐渐减小、最终趋于稳定的趋势。同时, 下游侧断层的能量耗散率峰值出现时间晚于拱肩断层的, 表明拱端推力在地基中的传递需要时间, 对结构面稳定性态的扰动作用存在一定的时空滞后性。与拱端下游侧相比, 拱端上游侧断层受水荷载引起的工程扰动的影响较小, 而下游侧断层的薄弱部位主要分布在与拱端相交处及沿断层产状延伸的下游侧区域。左岸的f123和f120断层为影响拱坝-地基整体稳定的关键断层, f123断层的2 440~2 470 m高程区域和f120断层的2 395~2 425 m高程区域为相对薄弱的关键加固部位。基于坝体位移、断层屈服区、能量耗散率及其域内积分指标的对比分析表明, 加固处理对拱坝-基础的整体稳定具有一定的改善作用。

Objective: High arch dams impose stringent requirements to ensure safety, requiring robust bearing capacity, deformation control, and resistance to seepage failure. The stability of the dam foundation serves as the cornerstone of the entire arch dam system. During operation, the enormous thrust generated by arch abutments acts on the dam-foundation interface, potentially inducing instability risks such as macroscopic fractures and shear sliding, particularly in weak foundation zones. These risks, if left unchecked, can compromise dam safety and may trigger catastrophic failure. Addressing weak zone reinforcement design in complex dam foundations poses a significant challenge, as no standardized system currently exists for prioritizing reinforcements or quantifying stability evaluation indicators. Methods: To address this gap, this study proposes an energy-based method for stability evaluation and reinforcement design of weak dam foundation zones. A stability evolution analysis model was established using energy dissipation rate and domain integral variation, enabling the identification of critical weak zones and their evolutionary patterns. The study employed a three-dimensional numerical model of the arch dam-foundation system, accounting for complex geological factors such as faults, abutment slopes, and dam geometry. A thermodynamically driven creep constitutive model with internal variables was employed to conduct three-dimensional numerical simulations, revealing the stability evolution process of weak foundation zones. By analyzing energy dissipation rate curves and domain integrals, critical moments (marked by peak dissipation rates) and vulnerable areas (highlighted by energy concentration zones) were pinpointed. This method was then applied to parallel fault groups in a high arch dam foundation, with the reinforcement effectiveness analyzed in terms of energy dissipation rates, dam deformation, fault yield zones, and results from comparative testing using the super-water unit weight method. Results: Results indicate that energy dissipation rates and domain integrals for abutment faults initially increased rapidly after reservoir impoundment, gradually decreased, and eventually stabilized. The stability evolution of dam foundation faults under impoundment exhibits distinct time-dependent behavior, progressing through three phases: instability, transition, and stabilization. A significant observation is the delayed occurrence of peak energy dissipation rates in downstream faults, reflecting a spatiotemporal hysteresis in arch thrust transmission. During normal operations, the thrust from the arch extends its influence on deep foundation stability to a distance approximately twice the width of the arch abutment. However, its impact on downstream stability ranges between 2-3 times the abutment width. Comparative analysis using the super-water unit weight method demonstrated reduced dam deformation, improved fault yield zone distribution, and significant decreases in energy dissipation rates and domain integrals for critical faults after reinforcement. Conclusions: The proposed method reveals spatiotemporal hysteresis in arch thrust transmission and its disturbance on structural stability. For multifault dam foundations, upstream faults exhibit less susceptibility to hydraulic disturbances when compared to downstream faults. Weak zones in downstream faults are primarily concentrated near their intersections with the dam abutment as well as along the strike direction. The f123 and f120 faults on the left bank were identified as critical to global stability, with key reinforcement areas at elevations of 2 440-2 470 m (f123) and 2 395-2 425 m (f120). Targeted reinforcement measures effectively enhanced fault and foundation stability, significantly improving the overall stability of the arch dam-foundation system.