Performance of Prestressed Anchor Cables Supporting Deep Foundation Pit of a Subway Station during Spring Thaw

Abstract

Based on the deep foundation pit for a subway station in Changchun (China), a 3D numerical model of water–heat coupling in a prestressed pile anchor system was established to determine its performance in freezing and thawing seasons in alpine areas. Its reliability was confirmed using field monitoring data on the prestressed anchor cables, which demonstrated changes in surface subsidence, anchor cable axial force, and pile horizontal displacement during spring thaw. The results demonstrated different degrees of elevation of the ground surface at the beginning of the spring thaw depending on whether the ground surface was at 2, 5, or 8 m from the pit excavation surface. Moreover, they demonstrated the occurrence of melting and surface subsidence when the temperature rises above 0°C, and that the axial force of the anchor cables fluctuates at the beginning of spring thaw but stabilizes in its middle and late stages. The phenomenon of pile horizontal displacement during the spring thaw could be roughly divided into three stages, with the second stage resulting in the most significant displacement. These results can provide certain reference for deep foundation pit projects in alpine areas.

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

“…Based on the measured data, a general apparent earth pressure envelope of earth pressure was proposed, as was an optimization scheme of diaphragm wall construction and design. Feng et al [20] proved that changes in surface settlement, the axial force of anchor cables, and the horizontal displacement of piles during the spring thawing process can provide a certain reference for the engineering of deep foundation pits in high-altitude and cold regions. Wang et al [21] believes that changes in the water level have a significant impact on the stability of the foundation pit, and has analyzed and optimized the grouting reinforcement parameters.…”

Supporting Mechanism of Pile-Anchor Systems for Deep Foundation Pits in Alpine Regions during the Spring Thaw

“…Dong and Yu proposed a numerical model to simulate the frost heave and stress of water pipes and performed experiments to confirm the reliability of the model at simulating the temperature distribution and volume variation [14]. Chou et al, Zhao et al, Han et al, and Feng et al used the software Geo-Studio and demonstrated that the thawing depth of slopes subjected to freeze thaw cycles increased with the freezing depth and that a closed loop isotherm formed on the slope [15][16][17][18][19]. Other researchers have used onsite monitoring, indoor freeze thaw tests, thermal parameter tests, and numerical simulations to examine embankments, cut slopes, rock masses, and tunnels in cold regions [20][21][22][23][24][25][26][27][28][29][30].…”