Pile responses to side-by-side twin tunnelling in stiff clay: Effects of different tunnel depths relative to pile |
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| Institution: | 1. Department of Civil Engineering, Quaid-e-Awam University of Engineering, Science & Technology, Sindh, Pakistan;2. Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Special Administrative Region;3. Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region;1. Department of Civil Engineering, University of Nottingham, University Park, NG7 2RD Nottingham, United Kingdom;2. Department of Civil Engineering, University of Khartoum, P.O. Box 321, 11111 Khartoum, Sudan;3. DICEA, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy;4. SAAD, University of Camerino, Viale della Rimembranza, 63100 Ascoli Piceno, Italy;1. College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, China;2. Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong;3. Department of Civil Engineering, Quaid-e-Awam University of Engineering, Science & Technology, Nawabshah, Sindh and Pakistan;1. Department of Civil Engineering, Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Ladkrabang, Bangkok, Thailand;2. Department of Civil Engineering, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, Thung Khru, Bangkok, Thailand;3. Department of Mechanical Engineering, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, Thung Khru, Bangkok, Thailand;1. Department of Geotechnical Engineering, School of Civil Engineering, Tongji University, Shanghai 200092, China;2. Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education, Tongji University, Shanghai 200092, China;3. Department of Civil, Environmental and Architectural Engineering, University of Colorado at Boulder, Boulder, CO, USA |
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| Abstract: | In densely built areas, the development of underground transportation systems often involves twin tunnels, which are sometimes unavoidably constructed adjacent to existing piled foundations. Because soil stiffness degrades with induced stress release and shear strain during tunnelling, it is vital to investigate the pile responses to subsequent tunnels after the first tunnel in a twin-tunnel transportation system. To gain new insights into single pile responses to side-by-side twin tunnelling in saturated stiff clay, a three-dimensional coupled-consolidation numerical parametric study is carried out. An advanced hypoplasticity (clay) constitutive model with small-strain stiffness is adopted. The effects of each tunnel depth relative to pile are investigated by simulating the twin tunnels either near the mid-depth of the pile shaft or adjacent to or below the pile toe. The model parameters are calibrated against centrifuge test results in stiff clay reported in literature. It is found the second tunnelling in each case resulted in larger settlement than that due to the first tunnelling with a maximum percentage difference of 175% in the case of twin tunnelling near the mid-depth of the shaft. This is because of the degradation of clay stiffness around the pile during the first tunnelling. Conversely, the first tunnelling-induced bending moment was reduced substantially during the second tunnelling. The most critical location of twin tunnels relative to the pile was found to be the tunnels below the pile toe. This is because the entire pile was located within the major influence zone of the twin tunnelling. Two distinct load transfer mechanisms can be identified in the pile, namely downward load transfer in case of tunnels near mid-depth of the pile shaft and next to the pile toe and upward load transfer in case of twin-tunnelling below the pile toe. These two transfer mechanisms can be useful for practitioner to assess the pile performance due to twin tunnelling. |
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| Keywords: | Twin tunnelling Pile Stiff clay Parametric study |
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