Analysis on intelligent deformation prediction of deep foundation pits with internal support based on optical fiber monitoring and the HSS model

Abstract

With the continuous expansion of the city scale, while rapidly advancing foundation pit construction, it has become a top priority to prevent the potential safety hazards caused by efforts to catch up with deadlines. In this case, deep foundation pit monitoring can provide important technical support for the foundation pit design and construction safety. However, conventional foundation pit monitoring for point monitoring of structural characteristics cannot accurately locate local strains and related cracks, and cannot provide real-time monitoring of support structures, ordinary soil constitutive models cannot consider the strain hardening characteristics of soft soil. This paper aimed to analyze the characteristics of excavation deformation of a deep foundation pit with internal support in the Dalian Donggang Business District by combining the methods of optical fiber monitoring and finite element simulation. In this study, distributed optical fiber monitoring and routine monitoring were adopted to carry out the synchronous excavation monitoring of foundation pit support structures. The main monitoring objects were the deep horizontal displacement of the support piles and the surface settlement of the foundation pit. Moreover, the authors used the Plaxis finite element software based on the Hardening Soil-small (HSS) model to conduct the numerical simulation analysis, and the results were compared with two groups of the measured data of the deep foundation pit obtained from the aforementioned research. Additionally, in light of the SSA-BP neural network, the back-analysis method of HSS model parameters in the Dalian area is proposed. The findings show that, under the premise of selecting reasonable parameters, the results of finite element analysis of the HSS model, considering the small strain characteristics of the soil, demonstrate a high degree of fit with the actual deformation law of foundation pits, which proves the rationality of the model. Furthermore, it was verified that the distributed optical fiber monitoring has conspicuous advantages in terms of data continuity and accuracy in contrast to routine monitoring. The research results of this paper can provide reference for deformation monitoring and early warning regarding the support structures of deep foundation pits.