RESEARCH ON FULL FRAMING CONSTRUCTION OF LARGE-SPAN DEEP EXCAVATIONS

To solve the problem of long duration and high cost of the changing-support scheme of large-span deep excavations，a new optimization method of replacing the scheme by full framing system was proposed． The finite element software MIDAS GTS 4. 0 and the finite element software SAP 2000 were respectively adopted to simulate whole construction processes of the two schemes of the large-span excavation pit project of axis J2 section of Nanjing Youth Olympics． The differences of these two schemes on side displacement of underground diaphragm walls， sedimentation of peripheral ground surface around the excavation，stress of underground diaphragm walls and axis forces of steel supports were analyzed， and the influence of the full framing scheme on the stress of main structure and full framing system was the focus of the analysis． Analysis results indicated that the deformation of supporting structure and the forces of supporting structure，main structure and full support system could meet safety requirements， so it was theoretically feasible to adopt the full framing construction scheme in this excavation project instead of the changing-support construction scheme．