蓄水初期特高拱坝及山体异常变形的机制与控制

At present, a number of super-high arch dams have been constructed and put into production in China. Abnormal deformation of the dam and slope are observed in several super-high arch dams after impoundment. How to analyze and explain the phenomenon, and how to evaluate structure safety based on such abnormal deformation is a common difficulty faced with the engineering and the academia. This project intends to focus on revealing the effective stress principle for unsaturated fractured rock mass and its applicability, and exploring the deterioration mechanism of fractured rock mass and structural planes during seepage. An unsaturated and unsteady coupling model of seepage and deformation is established to reveal the coupling effect and the temporal and spatial evolution of seepage field, stress field, deformation field, and to clarify the rule and mechanism of abnormal deformation during impoundment. Hydraulic fracturing induced by impoundment is studied, and the control scheme of impoundment rate is proposed. The interrelationship between abnormal deformation of the slope and operating behavior and safety of the dam is then explored to put forward a set of prediction method for abnormal deformation and safety control criterion for dam, providing a scientific basis for the safety during early impounding and long-term running.

近年来，我国若干特高拱坝蓄水期内出现谷幅缩小、库盆沉降等异常变形现象。它们的产生机理及对大坝工作性态的影响是目前坝工界和学术界共同关注的难题。为此，本项目采用宏细观相结合、数值模拟与物理模拟相结合、正演与反演相结合的研究方法，通过开展非饱和渗流作用下裂隙岩体变形机制、水对裂隙岩体及断层软弱带材料特性劣化规律等基础研究，揭示裂隙岩体非饱和状态下的有效应力原理及适用条件；建立边坡岩体非饱和非恒定渗流-变形耦合模型，揭示边坡内部渗流场、应力场、变形场的耦合效应及时空演化规律，阐明蓄水过程中边坡异常变形规律及机理；研究蓄水导致的水力劈裂效应，提出蓄水速率控制方案；开展地质力学模型试验，研究山体异常变形对特高拱坝工作性态和安全性影响规律，提出高坝及边坡异常变形预测方法及安全控制标准，为特高拱坝的初期蓄水安全和长期运行安全提供科学依据。

近年来，我国若干特高拱坝蓄水期内出现谷幅缩小、库盆沉降等异常变形现象，成为当前坝工界和学术界共同关注的热点难题。针对该异常变形产生机理及对大坝工作性态的影响，本课题开展了系统研究，取得如下4方面重要成果：（1）揭示出孔隙塑性理论可以有效地定量描述谷幅变形的主要特征（包括锦屏一级和白鹤滩特高拱坝，以及锦屏一级的上抬变形），研究表明谷幅变形对高水头的敏感性源于比奥有效应力与塑性有效应力的不一致；溪洛渡与锦屏一级和白鹤滩谷幅变形的规律和量值有显著不同，通过不平衡力分析确定了控制溪洛渡谷幅变形的关键断层。（2）定量系统研究了多种复杂本构模型和复杂工况对谷幅变形机制的影响，包括流变损伤耦合机制、非饱和渗流、THM耦合、蓄水对基岩的冷却作用和对岩体与断层参数的弱化作用、施工过程影响等。（3）通过室内试验，研究了蓄水触发结构面的变形规律；通过地质力学模型试验研究了蓄水对边坡变形的影响规律。（4）系统研究了裂隙水岩作用效应及其理论模型，包括力学作用（有效应力）、物理作用（润滑作用、软化、泥化等）、化学作用（溶解、沉淀、离子交换、水化、水解、溶蚀等）。达到项目预期的研究目标。上述成果已全面应用于溪洛渡、锦屏一级和白鹤滩拱坝，为推动我国特高拱坝建设做出了贡献。