Wpływ obiektów głęboko posadowionych na strukturę strumienia filtracji wód podziemnych w obszarze wrażliwym na zmiany warunków hydrogeodynamicznych

Abstract

Impact of deep foundations on the groundwater flow structure in the hydrogeodynamically vulnerable area.A b s t r a c t. The progressive citification of urban spaces results in compacting buildings and deeper foundation of new objects, and even deepening of existing facilities – to obtain maximum use of underground space. This process significantly interferes with the geological environment, both in the local (single deep foundation objects) and district (linear objects such as subways, tunnels, sewage collectors, groups of deep foundation objects). In Warsaw, underground urbanization extends several dozen meters deep and reaches the upper parts of the Neogene deposits, often fully intersecting Quaternary deposits. The progressing urbanization, and in particular the cumulative influence of deep foundation structures, creates a new set of factors with a potentially significant impact on the hydrogeological conditions of the Quaternary aquifer,including also the deep-seated aquifer, so far not having placed under a direct hydrogeodynamic impact. This article presents an assessment of the impact of underground development on the groundwater flow structure, with a particular emphasis on the deformation of the filtration mesh as a permanent result of object built-in into the groundwater stream. The analysis is based on the real case study of the implementation of a building located in the area vulnerable to hydrogeodynamic changes, where additionally can occur a cumulative impact with underground subway tunnels. Model simulations of the building foundation impact on the hydrogeodynamic conditions of the environment were performed. The results of prognostic model calculations were compared with the observations of changes in the groundwater level during construction works. The results indicate slight, permanent changes in groundwater levels, an increase in hydraulic gradients and changes in water flow directions. The scope of the changes was considered safe for the environment and building objects, allowing even a deeper foundation, although not devoid of the need for a long-term observation of groundwater levels. The obtained results indicate the usefulness and utilitarianity of numerical modeling methods in the analysis of hydrogeological conditioning of deep foundations.