Analysis of Foundation Pit Deformation Characteristics of “Two Walls Combined into One” and Double Ring Bracing System

To study the influence of excavation with a double ring bracing system on the deformation behavior of the diaphragm wall and shallow foundation building outside the pit under the condition of “two walls combined into one”. Taking a foundation pit project in Nanning city as an example, the settlement of adjacent buildings, the horizontal and vertical displacements of the top of the diaphragm wall, and the lateral displacement of the diaphragm wall caused by the foundation pit excavation were studied by using the site monitoring data. The results show that the settlement of a building was greatly affected by its height, foundation form, buried depth, and distance from the foundation pit. The vertical deformation of the diaphragm wall was greatly affected by the exposure time of foundation pit excavation and adjacent buildings. The maximum vertical displacement of the diaphragm wall, V_WY, varies between –0.088%~ 0.083%H_e (where H_e is the excavation depth). The adjacent part of the diaphragm wall lateral movement presents a “convex cantilever compound” deformation form; Due to the effect of the pit angle, the diaphragm wall at the pit angle presents a “stepped convex” deformation form. The maximum horizontal displacement range of the underground diaphragm wall was 0.02%H_e~0.21%H_e, and the average horizontal displacement of the diaphragm wall was 0.085%H_e.