冻融循环下宁夏引黄灌区渠道冻土多物理场耦合机理及衬砌破坏规律研究

In the Yellow River irrigated area of Ningxia, both frost heave and thaw settlement are the main reasons for the frequently freezing damage of canal lining, which not only seriously affect the service life and anti-seepage effect of canals, but also restrict the development of irrigated agriculture economy. This project takes the frost injury of canal lining in Ningxia Yellow River irrigation as the research background.By concluding the shortcomings of multi-field coupling mechanism and failure rule of the channel lining system under freeze-thaw process, we present a new idea that is the frost heaving and thaw settlement are closely linked under freeze–thaw cycles. Therefore, considering the coupling factors such as damage constitutive model and mechanical mechanism of soil, water transfer, ice water phase change, large strain consolidation, nonlinear contact between soil and lining, etc., we will study the coupling problem of water, temperature, displacement and stress fields of the canal lining and the frozen soil foundation. The main research contents of the project are to establish a smoothed meshless damage model for coupled moisture, heat and stress field of frozen soil, a smoothed meshless model for larger-strain thawing consolidation of ice–rich frozen soil and a damage model of canal ling under freeze-thaw cycles. Accordingly, a multiple physical field coupling software of the canal lining will be developed. By using the models and the software, the interaction mechanism and dynamic coupling process of multiple physical fields will be investigated. The evolution characteristics of various physical fields and the failure rule of the system of frozen soil and canal lining will be revealed. This project will help to strength and develop the canal lining structure optimization and anti-freezing technology. It also will be conductive to the sustainable development of agriculture economy as same as the construction of farmland water conservancy of facilities in the irrigation area of Ningxia.

在宁夏引黄灌区，冻胀和融沉是渠道衬砌冻害频发的主要原因，严重影响渠道使用年限和防渗效果，制约着灌区农业经济的健康发展。本项目以宁夏引黄灌区渠道衬砌的冻害现象为研究背景，提出“冻融相连、不可偏废”的研究思路，在综合考虑土体损伤本构关系、力学机制、水分迁移、冰水相变、大变形固结、土与衬砌的非线性接触关系等基础上，建立渠道冻土水热力耦合损伤分析的光滑无网格模型、高含冰量的渠道冻土融化固结大变形光滑无网格模型、冻融循环下引黄灌区渠道衬砌破坏模型，开发衬砌渠道的多物理场耦合分析软件，探索冻融循环作用下衬砌渠道温度场、水分场、位移场和应力场的相互作用机理和动态耦合过程，揭示渠道冻土在冻融循环作用下各物理场的演化特征及混凝土衬砌的破坏规律。本项目将有助于加强和发展宁夏引黄灌区渠道衬砌结构优化和防冻害技术，为宁夏引黄灌区农田水利配套设施的建设和农业经济的可持续发展提供科学依据和理论支持。

宁夏引黄灌区渠道衬砌工程抗冻破坏问题严重制约着宁夏灌区农田水利配套设施的建设和农业经济可持续发展，是一个亟待解决且极富挑战性的问题。本项目首先基于径向点插值无网格法和显热容法，模拟了冻土含相变瞬态热传导问题，得到了Stefan问题中移动界面随时间的变化规律；然后从材料细观力学出发，推导了描述饱和冻土水分场、温度场和应力场的多物理场耦合模型，并建立了相应的无网格离散方程；第三，基于广义光滑应变技术，分别提出了两水平嵌套光滑无网格法和广义线性光滑梯度无网格法，从数学理论和数值实验两方面证明了这两种方法的变分一致性、精度、计算效率和鲁棒性，为无网格法求解多物理场问题奠定了一定的理论基础。第四，对含初始裂纹的衬砌混凝土的断裂力学问题，在传统无网格近似函数中引入内部扩展基函数，建立了两种内部扩展光滑无网格方法，数值模拟了复杂荷载条件下衬砌结构变形规律、裂纹尖端应力强度因子、裂纹动态扩展路径等问题。数值结果表明这两种方法是精确、高效和稳定的；第五、结合广义梯度光滑理论和扩展无网格法，分别发展了两水平嵌套光滑扩展无网格法、线性梯度光滑扩展无网格法和扩展无网格-光滑无网格耦合法。这些方法在复杂结构静、动态振动分析和各向同性材料静、动态断裂力学问题中均展现出高精度、高效和稳定的优势，不仅有助于夯实无网格法的理论基础，也推动了无网格法解决实际工程问题的能力。项目取得的主要学术成果：发表相关学术论文8篇，其中第一或通讯作者发表高水平论文7篇，出版专著1部，培养硕士研究生4名。