砂土地基中加筋深度效果研究

利用非线性弹塑性有限元对具有不同加筋层数砂土地基的一系列模型试验结果进行了较为全面的计算与分析。有限元解析中所采用的砂土本构模型以修正塑性应变能量为硬软化基本参量,它可以较为精确地模拟砂土的应力路径效果。作为解析对象的模型地基由干燥的日本丰浦砂组成,不同层数的加筋材平铺在条形基础下方。结果表明,利用这种精度较高的有限元解析方法对加筋砂土地基进行解析,可以较好地再现由于加筋层数(加筋深度)变化而带来的对承载力与变形的影响。尽管加筋宽度与基础宽度相同,但是随着加筋层数的增多,加筋砂土地基的承载力明显增大,加筋深度效果明显优于加筋宽板效果。另外,利用以上的有限元分析,也能合理地模拟砂土地基渐进性剪切破坏的现象以及加筋材的诱发引张内力,可以更加合理地认识和理解砂土地基中加筋深度补强机理。

DEEP-FOOTING REINFORCING MECHANISM ON REINFORCED SANDY GROUND

In order to investigate the deep-footing mechanism of reinforced sand,a series of results from plane strain laboratory model test with different number of reinforced layers,are simulated by a nonlinear FEM analysis incorporating an elasto-plastic constitutive model for sand. The constitutive model is developed to have a stress path-independent work-hardening parameter based on the modified plastic strain energy concept. The model ground is made of air-dried dense Toyoura sand,which is either unreinforced or reinforced with numbers of layers and vertical spacing of layers of linear,tensile reinforcing members placed horizontally beneath a strip footing. The results indicate that load-settlement relationships obtained by the FEM analysis are well comparable with those from the physical experiment. It is found out that the peak footing load of reinforced ground increases significantly with the increase of the number of reinforcement layers (the deep-footing effect),despite that fact the reinforcement length is the same as the footing width,and the contribution by the deep-footing effect is more important than that of the wide-slab effect. In addition,the results also indicate that the progressive failure of model ground with a development of shear bands and the induced tensile forces of reinforcement are reasonably examined by the present FEM analysis,and the deep-footing mechanism of reinforced sandy ground can be well understood.