Abstract: Based on previous statistics analysis on deep excavations with diaphragm wall as retaining structure in Shanghai, the deformation characteristics of dual-purpose diaphragm wall and impact on adjacent architecture outside are comprehensively studied through the analysis of field monitoring data of two typical and similar deep large excavations in soft soil region, as well as the effects of soft soil layer thickness in superficial stratum and excavation area. The research results show that: (1) The lateral displacement of retaining wall behaves as a parabolic curve during the construction. The deformation is almost generated in the excavation stage while the sequential deformation caused by the removal of struts is only about 10% of the amount of excavation stage. The thickness of soft soil layer in the depth of excavation has a great influence on the lateral displacement of diaphragm wall. (2) It is revealed that the thickness of soft soil layer can affect significantly not only on the maximum ground surface settlement and its location; but also on the acceleration of settlement and its stabilization. However, it will not change the groove shape distribution of ground settlement. (3) The upper of diaphragm wall and pillars are in uplift state; and the upheaval increases from the edge of the excavation to the middle during the construction. There is not a large difference for the upheaval between adjacent pillars in the middle of excavation; but it is relatively larger for the adjacent pillars at the edge of excavation. That difference boundary is about (1.0-1.5)He (He is the excavation depth) away from the edge of excavation. The thickness of soft soil layer and excavation area obviously influence great much on the upheaval value of pillars. (4) Especially, the type and depth of foundation and the distance away from the excavation contribute considerably to settlement of adjacent building outside.

Key words: deep excavation, dual-purpose diaphragm wall, diaphragm wall, deformation characteristics, field monitoring