环境影响下黄土边坡灾变力学机制的微-细-宏观多尺度研究

Due to the special structures and strong water sensitivity, the loess is easily softened by water and furthermore the landslide occurs under external engineering disturbances. These loess slope failures are attributed to the structure damages at micro-meso-macro scales with the combination action of water and external loads. Thus, the multi-scale research on the mechanics mechanism of loess slope failures has not only theoretical significance but also the engineering application value. Based on the detailed research of geological conditions, this project will focus on the typical loess landslides, through the quantitative analysis of loess micro-structure, soil mechanics experiments and physical model tests, to study the mechanism of loess slope failures with the knowledge of solid mechanics and rock-soil mechanics. The main topics are as follows: (1) With the particle interaction mechanism and micro-structural feature of loess, to establish loess microstructure quantitative model and the particles’ interaction modes, and reveal the slipping mechanism of particles’ contact interface; (2) with consideration of water-loess coupling action and external loads, to study the loess micro-structure evolution process and the failure mechanism at meso-scale, and establish the loess elasto-visco-plastic damage constitutive law as well as its strength theory; (3) to establish the loess’s pore-crack-joint medium structure model and permeability model, study the damage process of the loess slope and the mechanism of shear zone forming, finally reveal the disaster-causing mechanism of loess slope in micro-meso-macro scales. Through the study, it is expected to establish a set of systematic theories in loess landslides, and provide scientific basis for engineering construction and disaster prevention in the loess areas of China.

黄土特殊的结构特征、强烈的水敏性特点，使得黄土有遇水软化和工程扰动下的强致灾特性。这些均源于水、力作用下黄土的微-细-宏观多尺度结构破损，故开展多尺度黄土灾变力学机制研究具有重要意义。本项目以典型黄土边坡为对象，在地质条件研究的基础上，通过黄土的微结构定量化分析、土力学试验、物理模型试验等方法，并运用固体力学、岩土力学理论开展以下研究：（1）黄土微观结构特征及颗粒相互作用机理，建立黄土微结构定量化模型及颗粒相互作用模式，揭示颗粒滑移机理；（2）细观尺度下水土相互作用和荷载作用下黄土结构演化及破损机理，建立黄土弹粘塑性损伤本构模型及强度理论；（3）建立黄土边坡孔隙-裂隙-节理多重介质结构模型和渗透模型，研究环境影响下黄土边坡破损过程及剪切带形成机理，揭示环境影响下黄土边坡微-细-宏观灾变力学机制。通过研究，建立一套系统的黄土边坡灾害力学理论，为我国黄土地区工程建设及减灾防灾提供科学依据。

项目自获批以来，研究团队聚焦黄土灾变力学关键科学问题，紧密围绕研究目标和内容，从多尺度上开展了黄土灾变机制的系统性研究，在 “微结构模型和机制、细观本构和强度理论、宏观灾变机理”三个层面取得系列创新性成果。（1）微结构模型：提出了基于连续切片技术的黄土三维微结构观测方法；研制了水-力作用下黄土三维微结构动态观测技术装备；建立了黄土三维微结构定量表征理论体系；重构了黄土高原不同区域和地层的黄土三维微结构，揭示了微结构特征和类型的分布规律及成因机制。（2）微观力学模型：建立了颗粒间滑移、非滑移接触、水致滑移的力学解析解，揭示了黄土水、力作用下的微观滑移机理。（3）微观灾变机制：研究了水-力作用下微结构变化及剪切带演化过程，揭示了黄土的强度劣化和遇水软化机制。（4）本构和强度理论：针对黄土特殊力学性能，建立基于最大能量耗散率原理的弹塑性本构模型和二元介质本构模型；提出了双剪统一强度理论在黄土中的应用方法和强度理论参数取值范围。（5）宏观灾变机制：建立了适用于均质黄土的非饱和浸润锋渗流模型，揭示了均匀渗流作用下黄土斜坡侵蚀流滑破坏机制；阐明了结构性黄土优势流的渗透规律和影响效应，揭示了优先渗流侵入导致突发性滑坡的水力学机制；建立了黄土边坡剪切破损带萌生-扩展的断裂力学理论解；编制了扩展有限元程序，实现了边坡多尺度结构面协同的致灾过程数值模拟；阐释了复杂应力条件下黄土边坡的响应特征和渐进破损过程，揭示了重分布应力对塑性区迁移和扩展的驱动机制及宏观破损带形成机理。. 依托项目成果出版学术专著1部；发表学术论52篇（SCI 40篇、EI 3篇、CSCD 9篇）；授权发明专利2项、实用新型专利2项；培养博士8名、硕士12名；获陕西省科技进步奖一等奖1项。本研究实现了黄土灾害的多尺度、多层次的全链条突破，建立了黄土灾变力学理论体系。成果应用于大量黄土灾害的机制研究和安全评价，为黄土地区重大工程建设和国家战略实施提供理论支持。