基于DEM-FDM耦合的筋箍碎石桩承载变形特性研究

Study on Load-deformation Characteristics of Geosynthetic-encased Stone Column Based on DEM-FDM Coupling Method

采用离散元-有限差分耦合数值方法研究筋箍碎石桩承载变形特性。基于离散元法对碎石桩建模,可从细观上揭示碎石颗粒相互作用和荷载传递机理,耦合有限差分连续介质模型能提高计算效率且更好地反映复合地基应力应变特性。数值模型分析了加筋长度、黏土抗剪强度对荷载-沉降特征、桩周土侧向变形、桩体应力和接触力链的影响。结果表明:最优加筋深度的选择应考虑工程的允许沉降、土体强度等因素,对于允许沉降较小的工程,在满足地基承载力和沉降要求的前提下,可优先选用顶部筋箍碎石桩,对于可能产生较大沉降的地基,宜采用全长加筋;对于强度较高的软土地基,应考虑充分发挥桩周土侧向约束效应以及筋材环箍效应,可优先选用顶部筋箍碎石桩。

This paper adopted a discrete element method(DEM)and finite difference method(FDM)coupled numerical method to study the load-deformation characteristics of the geosynthetic-encased stone column.Stone column modeled by discrete element method can reveal the interaction of gravel particles and load transfer mechanism from a microscopic perspective.Coupling finite difference continuum model can improve the computational efficiency and better reflect the stress and strain characteristics of composite foundation.Influences of geosynthetic encasement length and surrounding soil strength on the load-settlement behavior,lateral deformation of the surrounding soil,distribution of the stress and contact force chain within the column were analyzed.The results indicate that the selection of the optimum encasement length should consider the allowable settlement of the project and the strength of the foundation.For the project with small allowable settlement,top partially-encased stone column can be selected to reduce the cost on the premise of meeting the requirements of bearing capacity and settlement.However,fully-encased stone column should be used for the foundation which may experience large settlement.For the foundation with high strength,to fully consider the lateral confining effect of surrounding soil and the hoop effect of geosynthetics,the top partially-encased stone column should be adopted.