湿陷性黄土微观力学特征及其路基沉降规律

Micromechanical characteristics of collapsible loess and its subgrade settlement law

依托朔州市南环路黄土路基改扩建工程,基于电镜扫描试验和颗粒流数值模拟分析,研究孔隙率的差异性导致湿陷性黄土微观结构特征及其应力变化规律。采用宏观数值计算方法,建立湿陷性黄土公路路基施工力学三维模型,研究公路改扩建工程湿陷性黄土路基沉降规律,探讨路基参数对新旧路基沉降的影响效应。研究结果表明:湿陷性黄土颗粒主要分为散粒和凝块,其颗粒接触关系主要有3种:支架接触、镶嵌接触以及分散分布,其中,支架接触结构受含水率影响最大。在不同围压条件下,不同孔隙率的湿陷性黄土试样在加载过程中经历了4个发展阶段,并且孔隙率对湿陷性黄土峰值剪切强度以及剩余强度影响显著。新旧路基最大沉降和变形受路基加宽宽度和路堑挖深高度影响,且保持同增同减的关系;地基强度越高,新旧路基沉降变形越小。地下水位越高,黄土的湿陷性越明显,新旧路基沉降越大。

Relying on the loess subgrade reconstruction and expansion project of Shuozhou South Ring Road,based on the scanning electron microscope test and Grain flow numerical simulation analysis,the microstructure characteristics and stress changes of collapsible loess caused by the difference of porosity were studied microcosmically.A three-dimensional model of construction mechanics for collapsible loess highway roadbed was established using macroscopic numerical calculation methods.The settlement law of collapsible loess roadbed in highway reconstruction and expansion projects was studied macroscopically,and the effect of roadbed parameters on uneven settlement deformation of new and old roadbeds was explored.The research results were indicated that collapsible loess particles were mainly divided into loose particles and agglomerates,and their particle contact relationships mainly included:support contact,inlaid contact,and dispersed distribution.Among them,the support contact structure was most affected by the moisture content.Under different confining pressure conditions,collapsible loess samples with different porosities went through four stages of development during the loading process,and the porosity had a significant impact on the peak shear strength and residual strength of collapsible loess.The maximum settlement and deformation of both new and old roadbeds were affected by the widening width of the roadbed and the depth of the excavation,and maintain a relationship of equal increase and decrease.The foundation strength was higher,and the settlement deformation of the new and old roadbeds was smaller.The groundwater level was higher,and the collapsibility of loess was more obvious,and the settlement of new and old roadbeds was greater.The higher the groundwater level,the more obvious the collapsibility of loess,and the greater the uneven settlement of new and old roadbed.