Numerical modelling of 16 m deep underground structure

摘要

In the past period a rapid building expansion in the city centre of Skopje has been witnessed. In most cases the structures are small administrative buildings which do not exceed 1500 m~2. The relatively small construction sites together with the problem of parking had forced the investors to use the underground. The deep excavation in particular, when greater depths are considered in built-up surrounding has proved to be a formidable engineering task. This paper briefly presents the numerical modelling process of 16 m deep underground structure with five underground floors on the narrow site (11.5 × 27.6 m) next to two existing buildings and a very frequent boulevard which leads to main City square. The proposed technical solution has been compelled by the restricted space available for construction and the settlement of the adjacent buildings. The excavation at all times will be secured by a diaphragm wall and top to down method of construction. In order to describe the effects of underground construction and excavation in top to down manner a numerical model described by finite element method has been used. Several calculations had been performed with different detailing level in order to obtain more realistic simulation of the soil-structure interaction in all stages of construction. The top to down method of construction in combination with diaphragm wall has many advantages but most important is that allows an underground construction in build-up areas where the depth is not a restricting factor. The computation of such system although numerically relatively cheap it has to be followed by detailed analysis for assessment of the influence from different loading situations and material behaviour. Finally, proposed retaining system looks for experience contractors and skilled workers with specific detailing and prefabrication of the elements. Beside the technical also the economic aspects are in favour of the proposed structure indicating a very cost effective solution.