基于密集分布式光纤光栅感测技术的基坑底部隆起研究

依托上海地铁轨道交通某地铁站工程,采用密集分布式光纤光栅感测技术(FBG)对深基坑开挖中坑内土体隆起、基坑上部结构沉降和中心立柱桩变形问题进行了研究,建立了基坑隆起剖面的光纤监测系统,获得基坑底部土体多场多参量随时空的变化。监测结果表明:FBG监测技术可以实现基坑开挖全过程的监测,能够获取从下到上不同深度处的土体的隆起量。基坑在开挖后,由于卸荷与土体的应力释放,底部土体的隆起会呈现中间大两侧小的现象,上部结构监测中也验证了这一点,布设在混泥土支撑上与中心立柱同一竖直方向的静力水准相较于两侧的静力水准产生了相对的隆起量。研究成果为实现基坑隆起的智能监测提供了技术支持,为基坑开挖的安全评价提供了参考依据。

Research on heave of foundation pit bottom based on dense distributed FBG sensing technology

Based on the project of a subway station of Shanghai metro,this paper studied the problems of soil heave,settlement of upper structure of foundation pit and deformation of central column pile in deep foundation pit excavation by means of dense distributed fiber Bragg grating sensing technology(FBG).A fiber-optic monitoring system for the heave profile of foundation pit was established to obtain the multi field and multi parameter variation with time and space of soil at the bottom of foundation pit turn.The monitoring results showed that the FBG monitoring technology can realize the monitoring of the whole process of foundation pit excavation,and can obtain the amount of soil uplift at different depths from the bottom to the top.After the excavation of the foundation pit,due to the unloading and the stress release of the soil,the uplift of the bottom soil will present the phenomenon of large in the middle and small on both sides,which is also verified in the upper structure monitoring.Compared with the static level of the two sides,the static level arranged on the concrete support and the central column in the same vertical direction produces the relative uplift.The research results provide technical support for the realization of intelligent monitoring of foundation pit heave and reference for the safety evaluation of foundation pit excavation.