颗粒介质力学特性与碎屑流致灾机理的研究

A granular material is a conglomeration of discrete solid particle, macroscopic particles characterized by a loss of energy whenever the particles interact. An example of granular materials in nature is the granular debris flow, which occurs very often in southwestern China since 5.12 Wenchuan earthquake. The inherent structure characteristics and thermodynamics of granular materials are closely related to their mechanical properties. In this proposal, we focus on the following key problems: 1) measuring and quantifying both strong and weak force chain networks, determining it spatial temporal evolution dynamics, realizing the correlations among deformations, solid-fluid transition, energy fluctuation and dissipations with mechanical and thermodynamics properties. 2) analyzing the energy fluctuations properties, especially proposing a new granular temperatures to represent the elastic energy fluctuations; choosing appropriate irreversible process and determining the corresponding transport coefficients; revising the so-called two-granular-temperature thermodynamics (TGT), and coherently describing the full range mechanical behaviours. 3) understanding the solid-fluid transition mechanism from structural analysis, TGT and mechanical behaviours; proposing critical values of structure evolution and thermodynamical failure criteria; applying to some granular debris flows analysis. 4) Summarizing a few typical large scale granular debris flows, conducting flume tests and numerical simulations, analyzing the process from deformation, failure, flow until final deposition. After validating TGT theory and verification the numerical code, the fundamental studies will be used to predict the occurrence of granular debris flows and flow process under realistic situations.

颗粒介质由大量离散的粗颗粒聚集而成，如自然界的碎屑堆积体。其长程无序、短程有序的结构和复杂的能量转化过程，决定了颗粒介质的独特力学性质。表征结构特征、构建非平衡热力学，将促进对力学性质的理解及碎屑堆积体致灾过程的认识。本项目拟：1) 探测和表征强、弱力链结构特征，确立结构时空演化基本特征，实现其与变形、固态-流态转变、能量涨落与耗散等动力学和热力学行为关联；2) 分析在外力作用下能量和应力的涨落特征，确定颗粒动理学温度和颗粒构型温度描述动能、弹性势能涨落的适用性，确定不可逆过程及输运系数，完善双颗粒温度热力学，全面描述力学性质；3) 从热力学、动力学以及结构演化综合揭示固态-流态转变机制，确定结构参量临界数值和热力学失稳条件，初步用于碎屑堆积体稳定性分析；4) 开展大型水槽实验和基于热力学的数值计算，分析碎屑流变形→失稳→流动→堆积全过程，校验理论和程序。

本项目开展了如下研究：1) 研究了强、弱力链结构特征，确立结构参数时空演化基本特征；2)确定颗粒动理学温度和颗粒构型温度描述动能、弹性势能涨落的适用性，完善双颗粒温度热力学，全面描述颗粒流流态；3) 从热力学以及结构演化综合揭示固态-流态转变机制，确定了热力学失稳条件，初步用于碎屑堆积体稳定性分析；4) 开展了物理模型实验，开展了红石岩大型碎屑流灾害的的数值计算，分析灾害的全过程。