Discrete element method study of hysteretic behavior and deformation characteristics of rockfill material under cyclic loading

Abstract

Granular geomaterials under different loading conditions manifest various behaviors, such as hysteresis. Understanding their hysteretic behavior and deformation characteristics is the basis for establishing a constitutive relation with excellent performance in deformation prediction. The deformation characteristics of crushable particle materials are analyzed through a series of cyclic loading tests conducted by numerical simulation. The hysteretic behavior is investigated from a particle scale. The increase in particles with contacts less than two may be responsible for the residual strain, and the particle breakage further promotes particle rearrangement and volume contraction. Both the accumulation of plastic strain and the resilient modulus are found to be related to confining pressures, stress levels, cyclic loading amplitudes, and the number of cycles. The plastic strain accumulation can be written as a function of the number of cycles and an evolution function of resilient modulus is proposed.

概要

目的

岩土颗粒材料在不同加载条件下表现出复杂的力学行为,如滞回性。理解和掌握其滞回行为及变形特性是建立具有良好变形预测能力的本构关系的基础。本文旨在研究循环荷载下堆石料的变形特性,分析试样产生残余变形的原因及导致加卸载滞回圈逐渐重合的细观机理,研究不同加载条件(围压、应力水平、加卸载幅度和循环次数)对回弹模量的影响,为建立适用于堆石料的本构关系提供理论指导。

创新点

分析循环荷载下堆石料试样产生残余变形的原因,揭示导致加卸载条件下应力滞回圈逐渐靠近并重合的细观机理;2. 提出综合考虑围压、应力水平和加卸载幅度影响的回弹模量函数表达式。

方法

采用离散元数值模拟方法对堆石料细观模拟参数进行率定,并开展不同加载条件的循环加卸载数值试验(图6和12);2. 研究循环作用下颗粒配位数、孔隙率及颗粒破碎行为,并分析产生残余变形的原因及导致加卸载滞回圈逐渐重合的细观机理(图9);3. 研究不同围压、应力水平、加卸载幅度和加卸载循环次数对塑性应变累积及回弹模量的影响,并提出考虑不同加载条件的回弹模量表达式(公式(14))。

结论

循环荷载条件下堆石料宏观应力和体变存在滞回行为,且与围压、应力水平、加卸载幅度和循环次数密切相关。2. 堆石料试样中无承载能力的颗粒的数量随循环荷载逐渐增加是产生残余应变的原因;孔隙率随循环次数增加呈缓慢变化并逐渐稳定,在宏观上反映为滞回圈逐渐重合。3. 根据围压、应力水平及加卸载幅度对塑性应变累积及回弹模量的影响,提出了综合考虑不同加载条件影响的回弹模量表达式。