Deep urban excavation and retaining structures with emphasis on the role of geotechnical testing and performance monitoring

Milad Zakeri Ziyarati¹

1) PhD student in Civil Engineering, Geotechnical Department, Islamic Azad University, North Tehran Branch, Iran

IOI Code : AAAA-ABZBED
Publication : Second International Conference on Civil Engineering, Architecture, Development and Reconstruction of Urban Infrastructure(icduconf.com)
Abstract :
    Deep excavations in urban environments are considered one of the riskiest geotechnical engineering activities due to the presence of sensitive adjacent structures, complex soil stratification, and high groundwater levels. The aim of this study is to explain the decisive role of accurate field and laboratory tests in the safe and economical design of retaining structures and to emphasize the necessity of continuous performance monitoring during construction. Common stabilization methods including nailing, ground anchoring, diaphragm wall, and truss bracing were reviewed and the advantages and limitations of each in different soil conditions were explained. Key in-situ tests such as standard penetration (SPT), cone penetration (CPT), blade shear, and plate loading, along with triaxial laboratory tests, consolidation, and grading, were introduced as the main inputs for finite element numerical modeling and probabilistic stability analysis. A case study of the deep excavation of the National Salvation Church in Bucharest (Romania), measuring 127 x 66 m and more than 16 m deep, stabilized with a diaphragm wall and prestressed anchors, showed that accuracy in interpreting the results of CPT and cyclic triaxial tests limited the horizontal displacements of the wall to less than 20 mm and the adjacent settlement to less than 15 mm. The results of this study indicate that the use of a limit state approach with partial coefficients, the combination of modern stabilization methods (such as jet grouting) and accurate instrumental monitoring (inclinometers, piezometers and settlement points) can reduce the implementation risk by 70% and ensure the safety and economy of the project at the same time.

Keywords : deep excavation guard structure in situ geotechnical testing diaphragm wall numerical modeling performance monitoring