Effect of assembled H-shaped steel struts with servo system on the safe excavation of a subway station

Abstract

An innovative design of assembled H-shaped steel struts (AHSS) with servo system is introduced for the deep excavation of a T-shaped subway interchange station in soft soil. Analysis of the field monitored axial force of the strut, horizontal displacement of retaining wall, ground surface settlement and displacement of the nearby existing tunnel showed that the servo system could provide a convincing stable axial force for each level of AHSS. When a new level of AHSS with servo system was put into operation, the axial force of the closest level of concrete strut above tended to be more greatly affected than the other levels of strut. The first level of concrete strut contributed much less to resisting horizontal displacement of the diaphragm wall than the other levels of strut, and was under tension during the later stage of excavation. The maximum horizontal displacement of diaphragm wall, displacement of the existing tunnel and ground surface settlement were all controlled well with the operation of AHSS with servo system. Meanwhile, stricter control of the horizontal displacement of the diaphragm wall in the early stage is considered to be beneficial to the control of further deformation of the excavation at a later stage.