Construction of Deep Foundation Ditch under a Reconstructed Multi-storey Building on the Main Avenue of St.Petersburg

Abstract

The reconstruction of the former administrative building of the beginning of the 19th century in the center of St. Petersburg on the main avenue and adaptation it to the modern Hotel is considered. The new 6-storey building is done as a concrete frame with max height 27,7 m. The underground floor 66,9 x 20,09 m for parking and technical rooms is planned under the whole area of the building. The 4-5 storey brick block of flats and 3-5 storey administrative building, the historical memorial, adjoin to the building under the reconstruction. The adjacent buildings have cracks and defects due to general wear, rigidity decrease of the building and low deformation characteristics of the soil. The soft water saturated soil under the basement become thixotropic under insignificant dynamic effect (transport, seasonal freezing and etc). Prior to dissembling the building it was done the monitoring of the adjacent buildings and the reinforcement of their foundations using the method of injecting cement grout into foundation and erecting 75 tilted anchor piles 25 m long, 200mm diameter according to “Titan” Technology. The protection walls of the excavated pit for underground space in the reconstructed building was done by metal sheet pile “Arselor 37-700”13,5 m long, boring piles 27m long and diameter 410mm. Additionally jet-grouting piles were erected to the depth min 2 meters from the footing of the existed foundation along the break walls of the adjacent buildings. While excavating the pit in order to provide the sheet pile stability, the strut from metal pipes was done. In order to make pile base under the frame of the building 162 bore piles 27 m long and diameter 550mm were used. The piles were made according to the Drilling Displacement System (DDS) technology. Scheme of constructive decisions are given. The monitoring during the foundation construction and the beginning of the upper part construction showed that the additional settlement of the adjacent buildings did not exceed 20mm, the limited allowance for this type of the building.