Selection of support system for urban deep excavations: A case study in Ahvaz geology

Today, the increased need for construction in congested urban areas has necessitated construction of tall and massive structures. In these cases, design engineers have the option of excavation and digging of undisturbed and fresh spaces under the ground. Due to the presence of urban structures and public facilities adjacent to the excavation sites, which in some cases are highly important, the use of a support system with good and safe performance that can prevent probable losses is essential. Therefore, various support systems can be proposed for stabilizing the excavations and their surroundings. Nevertheless, selecting an appropriate support system in urban areas that can increase the stability of excavations has been a long-time challenge for design engineers. Due to the variable geotechnical conditions in these areas, which occasionally cause extensive changes between soil layers within a close distance, the stress-deformation field is very complicated and extended, making it difficult to select and design a proper and safe support system. Therefore, in this study, after investigating different excavation methods in urban areas and comparing conventional and widely used methods in these areas, an appropriate and safe support system was proposed for excavation in urban areas depending on construction, structural and economic conditions. The behavior of a controlled excavation using the proposed support system in Ahvaz city which possesses variable and complex geotechnical properties, was investigated, and the displacement values during the construction and the progress of the excavation were examined and assessed. For a more precise investigation of the support system behavior, the performance of the support system was compared with other systems utilized in other projects in Ahvaz city. The obtained results indicated that application of a rigid system would have the best performance.