Abstract
The information about the engineering-geological conditions in the central part of St. Petersburg which are characterized by deep thickness of weak water saturated soil is given. Three buildings with large underground space constructed in St. Petersburg are considered as examples. The depth of each space exceeds 12 m and required the usage of modern and nonstandard construction and technological methods for protection of the ditch walls. The wall protection was done by sheet piles, by diaphragm wall method, and jet grouting method. The soil excavation was carried out by traditional method or top–down method. The basic constructive schemes and technological methods of ditch excavation, test results of deformation of the protection walls during excavation of the ditch and the settlements of the neighboring buildings are given.
