碎石土内侵蚀演化特性及作用机理研究

For the internal erosion phenomenon occurred in gravel soil slopes/landsldes,landslide dams, earth dams and other accumulation body, this project is focused on the research of the mechanism and the characteristics of the evolution of internal erosion in the gravel soil.Considering the current erosion simulation test equipment cannot meet the needs of large size wide grading gravel soil erosion experiment simulation，a suitable correspondent equipment must be prepared for large size wide grading soil erosion simulation, and then the simulation can be carried out under stress and hydraulic conditions. On the basis of a large number of test results with theoretical analysis and numerical simulation, the aim of the project is to solve the key scientific problems such as the characteristic relation between geometric conditions and gravel soil erosion evolution, the gravel soil erosion evolution rule under the action of stress and hydraulic conditions, the damage evolution mechanism for gravel soil stiffness and strength in different stages of erosion. By establishing the damage evolution analysis model and calculation method of the mechanical and hydraulic characteristics under the effect of internal erosion of the gravel soil and applying it to the typical engineering deformation damage and stability analysis, the model is improved with the on-site monitoring and feedback information constantly. Finally, the theoretical model and calculation method are established which is fit for the deformation damage analysis of the gravel soil under the internal erosion condition, and a scientific basis is set up for the deformation failure mechanism analysis and engineering management design in gravel soil slopes/landslides,landslide dams, earth dams and other accumulation body.

针对碎石土边（滑）坡、堰塞坝、土石坝等堆积体中普遍存在的内侵蚀现象，围绕碎石土内侵蚀演化特性以及作用机理的问题开展研究。鉴于当前内侵蚀模拟试验设备无法满足大粒径宽级配碎石土内侵蚀试验模拟的需要，拟研制适用于大粒径宽级配碎石土内侵蚀模拟设备，并开展应力及水力条件下碎石土内侵蚀演化试验模拟。以大量试验成果为基础，结合理论分析及数值模拟，解决碎石土几何条件与内侵蚀演化特征关系、应力及水力条件作用下碎石土内侵蚀演化规律、不同内侵蚀阶段碎石土刚度及强度的损伤演化机制等关键科学问题。构建碎石土内侵作用下力学和水力特性的损伤演化分析模型及计算方法，并运用在典型工程变形破坏及稳定性分析中。利用现场监测与反馈信息，不断完善分析模型。最终形成适用于内侵蚀作用下的碎石土变形破坏分析的理论模型及计算方法，为碎石土边（滑）坡、堰塞坝、土石坝等堆积体变形破坏机制分析、工程治理设计等提供科学依据。

内侵蚀作用是导致溃坝等工程事故及滑坡等自然灾害的主要诱发因素之一。在内侵蚀过程中，土体内部细颗粒在水的渗透力作用下穿过粗颗粒形成的骨架而流失，进而在土体内部形成孔隙率较高的裂隙或孔洞，产生优势通道，导致水流对土体的内侵蚀作用进一步加剧，造成土体力学参数的降低。因此，认识和掌握土体内侵蚀特性及作用机理，对于揭示土石坝、堤防和滑坡、泥石流等工程事故和地质灾害的破坏机理，以及防范、预警和治理由渗透破坏引起的土石坝破坏或边坡失稳，具有十分重要的理论意义和工程价值。.本研究工作综合运用理论分析、室内试验和数值模拟相结合的方法对上述几个问题进行系统深入的研究，提出了适用于天然碎石土内部稳定性预测的判定准则；研制了满足天然碎石土渗透侵蚀及剪切试验要求的应力应变双控制式三轴试验设备；提出了考虑变形条件下天然碎石土侵蚀量变化本构模型；推导了同时考虑变形和细颗粒流失的多孔介质孔隙度方程，并提出了内侵蚀作用下天然碎石土理论分析模型和数值方法；量化了内侵蚀作用对天然碎石土堆积体滑坡整体变形及稳定性的影响。该研究研究的主要创新性成果如下：.1.分析了土体颗粒组成特征与内部稳定性的相关性，提出适用于预测天然碎石土的内部稳定性的判定准则。.2.研制了可模拟大粒径宽级配碎石土内侵蚀过程的应力应变控制式三轴剪切渗透试验设备。采用此设备，模拟了天然碎石土在变形前后的渗透侵蚀过程，分析了内侵蚀作用机理及对土体性状的影响，提出了描述变形条件下天然碎石土渗透侵蚀量变化本构模型。该本构模型充分考虑的岩土体变形后的侵蚀量变化规律，更加符合工程实际。.3.通过理论分析和推导，提出了以侵蚀颗粒流失与土体变形双向作用为耦合机制的多场流固耦合模型。.4.以三峡库区典型碎石土堆积层滑坡为模拟对象，采用数值分析的方法，模拟了长期稳定库水位工况和库水位涨落条件下滑坡体内侵蚀作用过程，量化了内侵蚀作用对堆积体滑坡整体变形和稳定性的影响。