黄土水敏性的力学机制及致滑机理

Loess is a special type of soil with water sensitivity, making water the most active triggering factor for loess landslides. Therefore it is a vitally fundamental problem in geo-hazards mitigation to study the mechanical mechanism of water sensitivity of loess and the induced loess landslides. Under the guidance of the theories of system engineering and suction stress-based unsaturated soil mechanics, this project will use multiple methods and focus on the unique water sensitivity of loess, aiming to reveal the essence of wetting phenomena such as disintegration, collapse, flow, build up index system of water sensitivity of loess, reveal the mechanical mechanisms of water sensitivity of loess. Then the project will also quantitatively depict the process of water influx–preferential infiltration-seepage diffusion-loess landslide initiation. The coordinating response mechanisms of groundwater dynamic system and slope stress system under water infiltration process will be explored and the theories of water-induced loess landslides will be developed. On the basis of above, the project will establish failure mechanism-based precipitation induced loess landslide hazard evaluation technique and warning model. According to the coordinating response mechanisms of groundwater dynamic system and slope stress system, develop key methodology of water level management-based loess landslide risk mitigation, and then solve water-induced loess landslide disaster problems with water treatment as the core, providing new theories and key techniques for disaster mitigation and prevention as well as urban and ecological civilization constructions in loess regions in China.

黄土是具有“水敏性”的特殊土，水是诱发黄土滑坡最积极的因素，黄土水敏性的力学机制及致滑机理研究已成为地质灾害防治中迫切需要解决的重大基础问题。以基于吸应力的非饱和土力学理论为指导，以黄土特殊的水敏性为切入点和突破口，通过多学科联合手段，研究黄土的土水特征函数和渗透系数函数等水敏性表征指标，探索基于黄土水敏性指标的黄土新型分类方法，揭示黄土水敏性的力学机制；定量刻画水的汇集—优势入渗—渗流扩散—发生黄土滑坡的过程，探索水体入渗过程中的地下水动力系统和斜坡应力系统协同响应机制，发展水致黄土滑坡理论。在此基础上，针对不同黄土斜坡地质结构和坡型，依据渐进破坏原理和有限元方法，建立基于含水率和吸应力的水致黄土斜坡稳定性评价和气象预警模型，提出风险防控关键技术，解决以治水为核心的水致黄土滑坡灾害防控问题。为我国黄土地区减灾防灾、城镇化和生态文明建设提供新的理论与关键技术。

黄土具有广泛的水敏性，水是诱发黄土滑坡最积极的因素，开展黄土水敏性力学机制及致滑机理研究是保障黄土高原地质与生态安全的核心基础问题。本项目系统性地开展了黄土水敏性力学机制及其分布规律、黄土优势入渗模式与物理过程、水致黄土滑坡机理与稳定性分析，以及基于控水的黄土滑坡风险减缓技术等研究，在理论创新、技术研发和应用实践方面取得了重要成果。主要包括：. ①揭示了黄土水敏性时空变化规律及其灾变力学机制。基于近千组非饱和试验测试结果，发现了在黄土高原空间上，从东向西、由南向北，时间上，沉积年代由老到新，黄土水敏性逐渐增强的变化规律。通过微观吸应力作用本质、中观空隙结构压密、宏观形变等黄土水敏力学行为试验，揭示了随着黄土含水率增大（或减小）引起吸应力锐减（或剧增）是黄土水敏性的力学本质，提出了基于吸应力的黄土水敏性灾变力学机制。. ②提出了黄土斜坡水分入渗模式，定量刻画了优势入渗的物理过程。基于多参数传感器的原位灌溉与降雨下的水分入渗分布式监测试验，发现了黄土斜坡水分均匀入渗-优势入渗-灌入扩散的3种入渗模式及其迁移规律。. ③发展了基于水力耦合-渐进破坏的黄土滑坡精细化预警技术。依托野外基地获取的不同坡型和不同坡度含水率数据、雨量数据，揭示了黄土高原6种水致黄土滑坡致灾机制，建立了以失稳概率为判别标准的黄土滑坡早期识别与精细化预警模型及预测方法。. ④建立了基于控水的黄土滑坡风险减缓技术方法。提出了以控“水”为主线的黄土地质灾害风险防控一体化技术，拓展了地质灾害防治解决方案。. 综上，通过本项目的研究，一方面为黄土高原减灾防灾和生态文明建设提供了新的理论与关键技术；另一方面丰富和完善了现有的黄土地质灾害防治技术方法，并对未来基于大数据智能混合优化的黄土地质灾害风险防控体系建设和相关前沿研究提供了海量数据支撑。