黄河坝岸散抛根石水流冲揭机理研究

The measures of bulk throwing stones for protecting slope root are crucial to maintaining the slope safety of dangerous engineering in the Regulation Project of Yellow River. The scouring and missing of bulk throwing root stones in flood period were closely related to deposit morphology and hydrodynamic characteristics, etc. But the theories of the stones missing were only studied on the relation between the motive force and the velocity of single stone at present. The missing mechanisms of root stones body were still empirically explained mostly. The definition of complex hydrodynamic boundary scattered around the stones body and missing process simulation method were lacked, thus these restricted the development of river regulation engineering reinforcement technique seriously. So the detailed study should be carried out as the following: (1) With the influencing factors of impact time and frequency of continuous flow considered, the flow force formula of sphere is improved, the current dynamic boundary functions of bulk throwing stones body are founded. (2) Utilizing the discrete element method, the discrete and missing developing rules of root stones are studied. And the methods of physical experiment are used for verification, the relevant relation between root stones discrete and different factors is revealed, thus the mesoscopic mechanism of root stones lost is explored. These research results will not only have important theory definition for the missing mechanism of bulk throwing root stones body, but also lay a foundation for the development of the non discrete mechanics theory about continuous medium for underwater. The research results will contribute to the scattered projectile reinforcement technology application and development in river regulation and flood control engineering.

散抛石护根措施对维护黄河河道整治工程坝岸安全至关重要。中常洪水期散抛根石表层冲揭走失与根石体堆积形态、水流动力特性等因素密切相关，但目前坝岸根石走失理论多数仅考虑单一块石起动力与流速关系，根石体受水流冲揭影响的走失机理仍停留在经验性解释，散抛体周边复杂水动力边界定义及走失过程模拟方法的不足，严重制约了河道整治工程加固技术的应用。为此将重点研究：(1)考虑水流持续冲击时间及冲击频率的强度因子影响，改进球体水流作用力公式，建立散抛根石体水流动力过程表征边界函数；(2)借助离散元理论方法，研究根石散抛体离散及走失发展规律，利用物理模型试验手段进行验证，揭示根石体离散与各影响因子的相关关系，据此探究根石体冲揭走失细观机理。研究成果对阐明坝岸根石散抛体走失机理具有重要的理论意义，并为水下非连续介质离散力学理论的发展奠定基础，将有助于推动散抛体加固技术在河道整治工程及防汛抢险中应用。

散抛石护根措施对维护堤防护岸工程安全至关重要。散抛根石表层冲揭走失与水流动力特性、根石接触摩阻力等因素密切相关，但目前坝岸根石走失理论多数仅考虑块体起动力与流速关系，而在散抛体周边复杂水动力边界定义及走失过程模拟方法等方面研究仍显不足，制约了根石加固技术有效性的分析。项目的主要研究内容及成果如下。.（1）利用基础水槽开展水流冲刷试验与力学计算分析，考虑了块体雷诺数、块体形状、水流冲击时间、冲击频率等影响因子，改进球体水流作用力公式，建立根石推移力、上举力、漩涡力等受水流脉动影响的过程表征函数，提出受河流冲揭影响的散抛根石非连续材料的水力学边界条件。.（2）开展水下堆积块体摩擦力试验与分析，并基于岩体结构面抗剪强度综合评价理论，分析水下块体间抗剪强度与结构面摩擦角、壁岩强度、粗糙度系数的相关关系，建立饱和块体间离散破坏模型。.（3）开展黄河典型险工坝岸1:100的正态模型试验，分析不同流场条件下，水流流速与根石走失断面坡度、方量的相关关系。基于FLOW-3D及PFC软件，融入改进的水力学边界条件，以饱和块体间离散破坏模型为判据，模拟基础水槽及坝岸冲刷模型试验的过程，反复验证并优化模拟方法，揭示坝岸走失现象及过程，建立一套散抛根石离散体失稳理论与物理试验验证方法。.研究成果对揭示坝岸根石散抛体走失机理，完善水下非连续介质离散力学理论具有重要的学术价值，并将有助于增强散抛体加固技术的有效性，为河道整治工程设计、防汛抢险预案的制定提供理论依据。