关键词: 基坑监测;围护结构;光纤传感器;光纤布设方法;位移计算;

Abstract: In order to solve the problems of prominent large deformation and difficult construction of shallow-buried section of tunnel entrance under water-rich condition, based on the Dongfengshan tunnel project under construction in Fuzhou City, the failure characteristics and causes of large deformation of tunnel section were analyzed in detail, and the corresponding countermeasures were put forward. The results showed that the large deformation was mainly caused by vault settlement due to the influence of stratum, topography, water environment and construction, and the deformation increased sharply in a short time after excavation. The large deformation of tunnel section presented a three-stage change rule of 'rapid growth, slow growth and stable trend'. The rapid growth stage was mainly concentrated before the next step excavation, and the deformation of surrounding rock accounts for about 75 %~80 % of the whole settlement deformation. According to the analysis of large deformation, it was proposed that the auxiliary reinforcement measures of 'advanced curtain grouting with well point precipitation' should be adopted before excavation, to improve the construction environment of surrounding rock in front of the working face. During excavation, the steel frame type strengthening, large-diameter locking foot at middle and lower steps and large arch foot at upper steps should be adopted, which can control the development of large deformation of tunnel to a large extent and ensure the safety of tunnel construction. The relevant experience can be used for reference in similar projects.

Key words: shallow-buried tunnel under water-rich condition; large section tunnel; large deformation; vault settlement; countermeasures; Dongfengshan tunnel