中心岛式支护在某基坑工程中的应用

Application of center-island retaining method to an excavation

内支撑和锚杆是两种为桩、墙式支护结构提供约束的方式,各有其特点和适用范围。当受周边环境限制,不能采用锚杆、而采用内支撑又不经济时,可以采用中心岛式支护方案。某基坑工程深19.11 m,基坑东侧6 m处有一16层住宅楼,为保证基坑稳定及该建筑物的安全,该部位采用中心岛式支护方案,进行二次开挖。第一次开挖时在该部位放坡预留土台,保证基坑的稳定,且将周边住宅楼的附加变形控制在允许的范围内。基坑开挖到底后进行主体结构施工,主体结构施工至±0.00后,再进行二次开挖。第二次开挖时在支护桩与主体结构之间设置三道内支撑,并设置一道锚杆,分步挖除留下的土台。基坑工程施工的过程中对支护结构及住宅楼进行了变形观测,支护结构的水平位移及住宅楼的沉降满足变形控制的要求。实践证明采用中心岛式支护是成功的。

They are two ways to add supports to retaining structure, and they are struts and anchors which have their own features and ranges of application. The center-island retaining method can be used, in case the anchors cannot be used and it is not economical if the struts are used. An excavation is 19.11 m deep, and there is a 16-storeys building 6 m to its east. The center-island retaining method is used in order to keep both the excavation stable and the building safe. At first, the earth is excavated with a slope at this part, so the reserved terrace can keep the retaining structure stable and control the additional deformation of the building in allowable range. The major structure is built after earth excavation is finished. The secondary excavation does not start until the major structure is built to ground surface, and three layers of struts and one layer of anchors are set in order to excavate the terrace. In the process of the excavation construction, both the displacement of retaining structure and the settlement of the building are monitored, and both of them are less than the allowable value. The engineering practice illustrates that it is successful to use the center-island method for this excavation.