格栅式地下连续墙竖向载荷模型试验研究

MODEL STUDY OF THE VERTICAL BEARING BEHAVIOURS OF LATTICE SHAPED DIAPHRAGM WALLS AS BRIDGE FOUNDATIONS IN SOFT SOIL

格栅式地下连续墙(以下简称:格栅式地连墙)作为一种新型的桥梁基础,为高铁软土地基处理提供了新的技术方案,然而目前其竖向承载机制的研究尚处于起步阶段。通过室内相似比为1∶30竖向载荷试验,对软土地基中的单室、两室与四室墙基础进行研究,试验结论表明:3种基础的Q-s曲线均为缓变型,且随着格室数目的增加,格栅式地连墙的极限承载力得到了提升,但并非呈线性增长;外摩阻力的发展与变化主要与墙–土相对位移及土性参数有关;基础内摩阻力基本呈上小下大的"L"形分布,且基本发挥于墙端以上约占墙体深度1/4的界限内,内摩阻力的发挥与内部格室尺寸有关,格室尺寸越大,越能调动基础内部摩阻力的发挥;基础的承台土反力发挥程度十分有限,总体呈"马鞍形"分布,并可忽略其对基础承载力所产生的贡献;加载过程中,基础均存在由"端承–摩擦墙"转变为"摩擦–端承墙"的趋势;在基础埋深与墙厚一定时,采用格室数目较少的基础形式,相比扩大格室尺寸大小,将对削弱基础的"群墙效应"起到更好的作用,从而使基础取得较好的承载效能。

As a new type of bridge foundation, the lattice shaped diaphragm wall(LSDW) provides a potential new solution to the problem of bridge foundation in soft soil for the construction of high-speed railways. In this paper, three LSDW foundation models with one, two and four chambers respectively were studied using an indoor test model having a similarity ratio of 1:30. It was found that the Q-s curves of all three LSDWs show the characteristics of gentle variation in settlement, and the ultimate bearing capacity of LSDWs increases non-linearly with the growth of material consumption and the number of chambers. The outer skin friction is related to soil properties and the relative displacement between the wall and the soil. The inner skin friction arises from the bottom of the wall, extending up to 1/4 of its depth and showing an 'L' shaped distribution. Its influence on the bearing capacity becomes more significant as the lattice size increases. The direct soil resistance to the LSDW foundation is relatively small and its contribution to the ultimate bearing capacity of the foundation can be ignored. During the loading process, all three LSDW foundations show the change from an end-surface bearing to a friction bearing dominant wall. At the same depth and wall thickness, adopting fewer chambers in the LSDW foundation, compared with using a larger chamber size, is more effective at weakening the combined effect of wall groups and achieving a better bearing performance of the foundation. © 2015, Science Press. All right reserved.