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

Abstract

This study investigated the supporting mechanism of the retaining piles and prestressed anchor cables of a deep foundation pit in alpine regions during the spring thaw. A numerical model was developed based on a subway project in Changchun City. Field monitoring data and the numerical model were used to analyze the variations in the ground settlement, horizontal displacement of the pile tops, and axial force of the anchor cables during the spring thaw under different working conditions. The results demonstrated that changes in the ground settlement primarily occurred in the late stages of the spring thaw with no obvious settlement phenomena because of the thaw. The pile top displacement of most piles remained stable. The axial force of the anchor cables gradually decreased and then sharply increased early in the spring thaw and then slowly decreased in the middle and late stages. Increasing the pile length decreased the pile top displacement to a certain point. Moreover, increasing the pile length increased the axial force of the first anchor cable but decreased the axial force of the lower four anchor cables. Furthermore, increasing the pile spacing increased the pile top displacement and axial force of the five anchor cables. Increasing the incident angle of the anchor cables decreased the pile top displacement and increased the axial force of the first, third, and fourth cables. The axial force of the second cable was minimized at an incident angle of 14°, and the axial force of the fifth cable was minimized at incident angles of 16° and 18°.