振动荷载下级配碎石颗粒运动及其能量特征试验研究

Laboratory investigation on meso-scale particle motion and kinematic energy characteristics of unbound aggregate base materials subjected to vibratory loading

大空隙级配碎石因其良好的透(排)水性能逐渐用作“海绵城市”路面结构的基层填料,但振动荷载作用下填料颗粒在重新排列过程中的运动姿态变化以及能量状态空间分布规律仍不明确。文章基于颗粒堆积理论设计了不同级配的碎石填料,开展不同激振参数组合下的室内新型平板振动压实试验,在试样内部不同位置处放置新型智能颗粒传感器(SmartRock)实时监测压实过程中颗粒的运动姿态变化,由颗粒加速度响应分析填料内部运动能量的时空演变规律,进而提出基于颗粒运动和能量分布的填料压实质量评价新指标。研究结果表明,级配碎石填料振动压实过程可明显分为两个不同阶段:第一阶段大部分能量耗散于碎石颗粒的竖向运动及空隙的压缩,占主导的颗粒竖向运动未形成致密的骨架结构;第二阶段颗粒主要发生水平面内的平动以及竖直面内的滚动,颗粒的长轴取向逐渐趋近于“平躺”状态,大部分能量耗散于颗粒间空隙的填充,颗粒逐渐互相紧密咬合嵌挤并形成稳定的骨架结构。试样中上部颗粒的运动指标可较好地评判压实状态,当颗粒水平向运动能量从逐渐增大过渡到逐渐减小至几乎没有任何能量分布但竖向能量分布突增时,表明试样已达到较优的压实状态,新的颗粒运动和能量指标可为连续压实质量智能评价和调控技术研究提供有益的理论依据和研究基础。

Unbound aggregate materials(UAM)featuring large air voids are increasingly used to construct pavement base/subbase layers for the initiative of sponge cities due to their desired drainage performance.However,particle motion and spatial distribution of kinetic energy during particle rearrangement process induced by vibratory loading are still not clear.This paper presents the results from laboratory vibratory plate compaction tests conducted on UAM specimens under different combinations of vibratory parameters with different levels of Gravel to Sand ratio(G/S),which is proposed previously from particle packing theory.The innovative SmartRock(SR)sensors were placed at different positions inside the specimen to monitor the real-time particle motion,whereas kinematic energy and its spatial distribution were analyzed from the acceleration time-history signals collected by SR sensors.To assess the compaction quality,a new index was proposed based on particle motion and kinematic energy. The results show that the vibratory compaction can becategorized into two distinct stages. In the first stage,the majority of the energy is dissipated by coarse particles movingmainly vertically and the compression of air voids,and the dense skeleton structure is not formed. In the second stage,coarse particles mainly translate in the horizontal plane and rotate in the vertical plane,and gradually tend to lie flat withlong axes oriented horizontally,while the majority of the energy is dissipated for filling air voids,thus leading to theoccurrence of densely packed skeleton structure. The particle movement and kinematic energy indices in the middle of thespecimen can be used to assess the compaction stage and quality. The particle motion in the lateral direction transitionsfrom continuously ascending to gradually descending to almost no kinematic energy,indicating that the specimen wascompacted to a relatively dense state. The research results can provide reference for intelligent assessment and control ofcontinuous compaction quality of UAMs.