STABILITY ASSESSMENT USING NUMERICAL MODELLING FOR LARGE UNDERGROUND SPACE IN URBAN AREAS FOR UNDERGROUND PARKING FACILITY AT METRO STATION

The existing use of underground space and further options of strengthening and integrating underground spaces into traditional planning process in urban areas has been surveyed through various studies and importance of underground spaces are explained in urban area. Urban underground space provide solutions for traffic congestion and here is such approach related to traffic congestion, lack of space, emission of pollutants through vehicles demanding for need of urban underground space. With increase in traffic and congestion scenario, metro has been playing vital role in metropolitan cities of India but there's always need for off-street parking like underground parking facilities at metro station considering the lack of space for parking, rise in motorized vehicles, congestion scenario in numerous urban areas of country. The underground parking station at metro station is going to be first of its kind in India. The various studies related to stability excavations, factors for underground parking, Deep excavations and working sequences are being studied and Top down construction Methodology adopted at urban area which has become a trend for its speed in execution. The numerical modeling was also done with respect to stability for respective geometry with basic soil parameters from a study. The Finite element modeling was done with RS2 2019 software. After detailed survey and on few assumptions two models were done for metro station which was dimensionally 32 mx21 m and to metro corridor for length of 200 m considering the plastic condition with 3 noded triangles with Mohr-Coulomb failure criteria. The Installation of diaphragm wall and struts are done with the sequential excavation i.e Top down construction methodology is adopted for 4 levels of excavation phases of underground metro station and are modeled for stability assessment. The stresses, displacements and strains were analyzed at excavation phases and diaphragm wall analysis is observed with geotechnical parameters and assigned loads. It ensured how important the thickness of wall, strut & its properties, meshing and loads played role in variation of stresses, displacements and strains in analysis for considered geotechnical conditions. These were analyzed and their variation is shown with values obtained by software. The strength reduction factor and inferences for both the models are observed, explained and also their variation is shown at initial and later stage of modeling. Conclusions were then taken up for need of underground parking facilities at metro stations and for underground space as they are need of the hour at urban places.