In situ axial loading tests on H-shaped steel strut with double splay supports

The design of a large excavation using a braced wall system (BWS) with H-shaped steel (HS) struts is introduced. In situ axial loading tests were conducted to study the load transfer and deformation mechanisms of an HS strut with double splay supports. The monitoring results indicate that the outer splay support withstands the most lateral earth pressure (48.5%), followed by the inner splay support (35.6%) and BC segment of the end support (15.9%). The safety redundancies of strength and stability for the outer and inner splay supports, AB and BC segments of the end support are all larger than 1.59. The axial deformations of the middle support and the whole strut tend to increase linearly with the loading process. Using the monitored total load of hydraulic jacks, the value of K_T″ of the whole strut is estimated to be 158–189 MN/m. The modified value of K_T″ (K_T″b_a/S) of the whole strut is 2.2–2.6 MN/m. It is close to the lower limit of the suggested range (2.5–3.5 MN/m) in the Chinese standard. The monitored data of typical safety control parameters during soil excavation and the monitored results during in situ loading tests indicate good performance of the BWS with HS struts in this project.