多层格栅加筋道砟界面联动‒互扰行为

Mutuality-Interference Behavior of Multi-Layer Geogrid Reinforced Ballast

摘要:

探究多层加筋土体系中筋材?道砟间合理间距对拉拔抗力的影响。通过改进传统单层格栅?道砟拉拔数值试验模型，实现了多层格栅等位移幅值下的同步拉拔的离散元模拟。数值模型采用刚性颗粒簇模拟道砟颗粒非球型特征，并运用黏结颗粒串模拟受力均匀的三向土工格栅，同时考虑了道砟颗粒间的嵌固效应和土工格栅的拉伸特性。以平均拉拔力、特定层位处界面强度与筋材应变为指标，科学识别多层格栅加筋道砟界面联动行为，并从颗粒尺度系统揭示了多层加筋体系层间互扰机制。结果表明，多层格栅的拉拔力和增长速率小于单层格栅，尤其在高法向应力下差异更明显，且存在不均匀性。随着加筋层数增加，筋材抗力差异显著，同时摩擦耗能增大。层间颗粒位移存在叠合，导致筋材宏观力学响应减弱，其内在原因是颗粒力链发育不够充分。法向接触力分析结果进一步表明，多层格栅加筋体系下的层间互扰可能导致法向接触力分布的不稳定性。

Abstract:

The influence of the appropriate spacing between reinforcement and ballast on the performance of pullout resistance in multi-layer reinforced soil structures were explored. By improving the conventional single-layer geogrid-ballast pullout numerical test model， discrete element simulations of synchronized pullout under equivalent displacement amplitudes for multi-layer geogrids were achieved. The rigid clump particles were used in the numerical model to mimic the non-spherical characteristics of the ballast particles， and bonded particle strings were incorporated to simulate the uniformly loaded triaxial geogrid， by considering both particle interlocking effects within the ballast and the tensile behavior of the geogrid. Using criteria such as average pull-out force， interfacial strength at specific layer positions， and strain in the reinforcement， the interfacial coupled behavior between multi-layer geogrid-reinforced ballast was scientifically determined， and the interlayer interference mechanism within the system was investigated at the particle scale. The results show that the pull-out force and its rate of increase in multi-layer geogrids are lower than those in single-layer geogrids， especially at high normal stresses， and there is non-uniformity. As the number of reinforcement layers increases， significant differences in the resistance of the reinforcement are observed， along with an increase in the frictional energy dissipation. Overlapping interlayer particle displacements weaken the macroscopic mechanical response of the reinforcement because of insufficient development of particle force chains. Subsequent investigation of normal contact forces indicates that inter-layer interference in multi-layer geogrid-reinforced structures may lead to instability in the distribution of normal contact forces.