塑料排水板地基侧向变形的模型试验与仿真分析

Model tests and simulation analyses on lateral deformation characteristics of PVD-improved ground

为探明不同预压模式下塑料排水板(prefabricated vertical drains,PVD)处理软土地基的侧向变形特性,以指导软土地区相关工程的设计与施工,通过室内大比例模型试验对比分析堆载预压和真空联合堆载预压下PVD地基的侧向变形特性。此外,结合有限元仿真分析,系统研究真空联合堆载预压下堆载速率(LR)、堆载大小(p_(s))和真空压力大小(|p_(v)|)对PVD地基侧向变形的影响规律。研究表明:真空联合堆载预压相较堆载预压可以匹配更快的堆载速率和更大的堆载,且达到最大堆载后的后续固结阶段,PVD地基的向外侧向变形并无明显增长,反观堆载预压工况,地基的最大向外侧向变形仍可增长达10%,局部深度位置侧向变形可增长超30%。真空联合堆载预压下PVD地基的侧向变形轮廓整体随p_(s)与LR的增加及|p_(v)|的减小而向预压区外侧移动,且地基的侧向变形速率及最大向外侧向变形(δ_(om))深度随之增加。此外,堆载施加过程中PVD地基的向外侧向变形呈阶梯型规律增加,其最大值δ_(om)近似随p_(s)增加而线性增大,随LR增加及|p_(v)|减小而非线性增长。同等荷载改变量下,|p_(v)|的改变相较于ps改变对地基侧向变形的影响更为显著。研究结果可为真空联合堆载预压处理软土地基的分析与设计提供参考。

To explore the lateral deformation characteristics of prefabricated vertical drains(PVD)-improved soft ground under different preloading loads and provide guidance for the design and construction of relevant structures in soft deposit regions,this study analyzed the lateral deformation characteristics of PVD-improved ground under surcharge preloading and combined vacuum and surcharge preloading using large-scale model tests.The influence of loading rate(LR),surcharge load(p_(s)),and vacuum pressure magnitude(|p_(v)|)on the lateral deformation of PVD-improved ground under combined preloading was systematically studied using finite element analyses.The results show that the preloading under combined vacuum and surcharge could match faster loading rates and larger surcharge loads compared to surcharge preloading alone.In the subsequent consolidation stage after reaching maximum surcharge load,there is aninsignificant increase in the outward lateral deformation of PVD-improved ground under combined preloading;in contrast,the maximum outward lateral deformation of the ground under surcharge preloading could still increase by 10%,and the lateral deformation of localization depths could increase by over 30%.The lateral deformation profile of PVD-improved ground under combined preloading overall moves outward with the increase of ps and LR,and the decrease of the|pv|;meanwhile the lateral deformation rate and the depth of the maximum outward lateral deformation(δ_(om))increase.The outward lateral deformation of PVD-improved presents step growth patterns during the surcharge loading process,and theδom increases approximately linearly with the increase of p_(s),but increases nonlinearly with the increase of LR and the decrease of|p_(v)|.With the same load change,the variation in|pv|has a more significant impact on the ground lateral deformation compared to the variation in p_(s).This study can provide basic information for the analysis and design of soft ground improvement under combined vacuum pressure and surcharge load.