According to the deep water foundations construction of Jishui grand bridge in Gan River,numerical simulation for the stress and deformation of the steel boxes is carried on by the finite difference software,and the safety and stability of steel boxes are also evaluated.In addition,the necessity of the concrete slab poured at the bottom of the steel box is demonstrated too.It is found that:1) the maximum horizontal displacement of steel boxes appears in the middle of the flank wall,and internal supports and the concrete slab play a great role in controlling the deformation of steel boxes;2) minimum principal stress is almost the compressive stress,which is mainly distributed in the four corner positions of steel boxes below the water level.Analyzing the stress and deformation of the concrete slab,it is found that,the deformation of concrete slab with the thickness of 80 cm is small,and it can satisfy the normal requirements and impermeability.Overall analysis shows that,stress and displacement do not exceed the warning value during the construction,and the concrete slab does play a good effect.However,because of the poor performance of the tensile properties of the concrete slab,there will be concentrated tension stress in the corner positions between the steel boxes and concrete slab,and it is very necessary to control the construction quality of the concrete.%结合抚吉高速公路B8合同段吉水特大桥深水基础施工的工程实际,基于有限差分软件对钢围堰在河底软弱地层施工中整体受力和变形情况进行了模拟分析,并对钢围堰结构的安全与稳定性进行了评价,同时也对钢围堰混凝土底板浇筑的必要性进行了论证分析.结果表明,钢围堰最大水平位移主要发生在侧墙的中部,内部横向钢支撑的对整个钢围堰的变形控制起到较大作用,混凝土底板的布设能够有效地控制钢围堰的内鼓变形;钢围堰最小主应力基本为压应力,主要分布在水位线以下的四个角点处.通过对混凝土底板的受力及变形情况分析表明,厚度为80 cm的混凝土底板变形较小,可满足抗渗及正常使用要求.总体分析表明,钢围堰施工过程中应力及位移计算结果均未超过警戒值,混凝土底板的布设能够起到较好的效果,但考虑到混凝土材料受拉性能较差,与钢围堰接触的四周角点部位易出现拉应力集中,因此应严格控制角点处混凝土的施工质量.
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