Monitoring and Prediction of Horizontal Displacement of Underground Enclosure Piles in Subway Foundation Pits

Abstract

Urban rail transportation and underground space development and utilization are initiatives to solve urban traffic congestion. The monitoring and prediction of the stability of underground enclosure piles in foundation pits is a key index for the dynamic evaluation of the stability of underground space engineering. In this paper, we focused on the problem that the dynamic prediction accuracy and stability of foundation pit retaining piles in the Qingdao area are not high. Based on the analysis of various time function curves and the physical meaning of the parameters, we proposed the Adjusted-Logistic time function model, which introduces three physical parameters to adjust the deformation velocity and deformation acceleration in different stages for better accuracy. It could predict the deformation process of underground enclosure piles under different geological engineering conditions. It was verified in the field that the root-mean-square error (RMSE) of the Adjusted-Logistic function was 0.5316, MAE was 0.3752, and R 2 was 0.9937, which were better than those of Gompertz, Weibull, and Knothe time function models. Meanwhile, it showed that with the increase of excavation depth, the maximum horizontal displacement of the underground enclosure piles gradually decreased and finally stabilized at 0.62−0.71 H. We established a catastrophe model of the horizontal displacement cusp at the observation point of the underground enclosure piles by using the time series of the measured data. It could determine the weak location of the underground enclosure pile stability and realize the multipoint warning of the foundation pit stability, which would ensure safe construction.

Numerical Simulation Study on Application of T-Shaped Composite Pile Support System in Super-Large Foundation Pit Support Engineering

“…The transfer of load can cause plastic damage to the beam, which requires consideration of the beam's position and construction excavation sequence to reduce the internal force of the beam structure and ensure the effectiveness of the support structure [22][23][24]. When the supporting structure is complex, using numerical simulation methods to study foundation pit excavation is easier to achieve than using on-site experimental methods [25][26][27][28][29].…”