基于动力过程的泥石流防治工程减灾效果量化评价研究

During the ten years after the Wenchuan Earthquake, a large quantity of debris flow prevention and control projects have been carried out in disaster-stricken areas. After being stricken by one or several debris flows, the effectiveness of these projects remains unknown, and thus a quantitative evaluation method is needed. To achieve this goal, the following works will be carried out in our proposed project. First, the project intends to choose the area of the frequent debris flow after Wenchuan earthquake as the research area, based on multi-source stereo disaster identification technologies, current status evaluations of the debris flow prevention and control projects will be conducted and a data base of these projects will be built up. Second, a reduced scale physical model test will be carried out to reveal the movement characteristics of the debris flows in the prevention and control structures and the rules underlying the variations the of parameters will be analyzed. Third, using solid-liquid phase flow theory, an evolutionary physical model simulating the movement of debris flows in the prevention and control structures will be built up. Fourth, based on finite volume method, a dynamic numerical computing platform which is takes the debris flow prevention and control projects into consideration will be established and the key indices of disaster reduction evaluation, such as the impact range of debris flow, depth of siltation, flow rate, and impact energy will be obtained. This study will help to realize a real-time quantitative evaluation of the effectiveness of the debris flow prevention and control projects, which may provide a scientific theory and technical support for the construction, management and maintenance of these projects.

汶川震后十年间，国家在地震灾区开展了大量泥石流防治工程建设，工程防治后（工后）的泥石流沟道又爆发过一次或多次泥石流，现有防治工程还具有多少减灾效果？迫切需要一套科学、合理的量化评价方法或平台。为此，项目拟选择汶川震后泥石流多发区作为研究区，开展泥石流防治工程现状调查及评估，建设研究区泥石流防治工程数据库；以典型工后泥石流沟道为原型，采用缩尺模型试验，揭示工后泥石流运动特征及各参数间的量变规律；利用固液两相流理论，构建工后泥石流运动演进物理模型,搭建考虑泥石流防治工程调控作用的动力学数值计算平台，获取工后泥石流运动范围、冲淤规模、能量时程（流深、流速、流量）等关键量化减灾效果评价指标，破解泥石流防治工程减灾效果的实时量化评价难题，为泥石流防治工程的建设、管理、维护提供理论及技术支持。

汶川震后大规模持续性泥石流是人类遇到的巨大挑战，震后即时开展的大量泥石流防治工程至今已运行多年，经过泥石流频繁作用后其防治工程部分或全部淤满，它们仍具有多少减灾效果？失去一定减灾效果的泥石流防治工程后期管理及维护依据何在？如何进行科学动态评价？这些问题是困扰工程界、科研界的难点问题，迫切需要一套科学、合理的量化评价方法或平台。数学、力学、数值模拟、试验设备的进步与发展，为重新认识地质灾害的防治工程体系建设、评价提供了新的思路、观念和手段，为工程界难点问题的解决提供新的机遇。为此，研究基于物理模型试验揭示了泥石流冲击拦挡坝的动力特征及各参数间的量变规律，并基于弱可压缩光滑粒子流体动力学方法（SPH），采用Drucker-Prager（DP）准则及Herschel-Bulkley-Papanastasiou(HBP）流变模型建立了考虑工程防治下的具有计算稳定、能适应复杂地形地貌的固液两相泥石流高效数值计算平台，并以红椿沟泥石流作为研究示范区，开展了泥石流拦挡坝减灾效果的实时量化评价。其次，提出了一种泥石流灾害防治新结构，即“开口柔性防护网”，推导了开口柔性防护网作用下泥石流速度衰减率、爬升高度和拦挡率的理论模型，基于物理模型试验验证了理论模型的可靠性并揭示了开口柔性防护网对泥石流的调控性能，最后以诺日朗泥石流沟作为研究示范区开展了泥石流开口柔性防护网减灾效果的量化评价。研究结果表明：针对泥石流拦挡坝，坝后淤积使拦挡坝削峰效应降低，显著降低其拦挡效果；同时坝后淤积改变泥石流冲击拦挡坝动力响应过程空库工况下泥石流表现出触坝、爬高、淤积等过程，满库工况表现为泥石流夹带淤积体过坝过程。自主研发的工程防治下的固液两相泥石流动力学数值计算平台可实时、高效量化防治工程的减灾效果。与传统闭口柔性防护网结构相比，开口柔性防护网起到了良好的自清洁作用，且可有效调控泥石流速度峰值；此外，泥石流拦挡率随着开口高度的增大而减少，而在相对开口高度（开口高度与网孔尺寸之比）达到 0.50 时，开口柔性防护网拦挡率降低显著。因此建议工程设计中柔性防护网相对开口高度应不低于0.50，以充分发挥开口柔性防护网自清洁作用；考虑实际工况下泥石流对柔性防护网的冲击磨蚀作用，建议实际工程中应采用双层甚至多层柔性防护网形式。上述研究成果可为泥石流拦挡工程设计、减灾效果量化评价提供理论及技术支持。