Performance of a Deep Excavation Supported by Diaphragm Walls Combining with Servo Steel Struts: A Case Study in Hangzhou, China, Soft Clay Deposits

As a novel type of supporting system, servo steel struts have been employed frequently in deep excavations adjacent to important infrastructures. However, the studies concerning the effect of servo steel struts on restraining deformation have not been consummated, and further detailed explorations are required. This study presents the performance of a deep excavation with servo struts based on on-site measurements, including wall deflections, ground settlements, and axial force of struts. To analyze in-depth the supporting effect of servo struts on restraining deformations, the wall deflections and ground settlements obtained from field observation are compared with those in existing studies. Furthermore, the behaviors of conventional struts and servo steel are numerically analyzed and compared. The results indicate that compared with conventional struts, servo steel struts can effectively bring the wall deflections caused by excavation under control. Installation of servo steel struts is an effective measure to reduce the rate of ground settlements but has little effect on the overall settlement trend. Different from the conventional struts, the upper part of the wall is pushed back by servo steel struts, resulting in a wall deformation in an S-shape and increasing the maximum deformation depth. The negative bending moments against the upper part of the wall are significantly greater than those supported by conventional struts.