Numerical analysis of pile response to open face tunnelling in stiff clay |
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| Institution: | 1. Ruhr University Bochum, Department of Civil and Environmental Engineering, Universitätsstr. 150, 44780 Bochum, Germany;2. Dr. Spang Ingenieurgesellschaft für Bauwesen, Geologie und Umwelttechnik mbH, Rosi-Wolfstein-Str. 6, 58453 Witten, Germany;3. Vössing Ingenieurgesellschaft mbH, Brunnenstr. 29, 40223 Düsseldorf, Germany;4. School of Civil Engineering, Sun Yat-Sen University, Guangzhou 510006, China;1. School of Civil Engineering, Central South University, Changsha, HN 410075, China;2. Department of Geotechnical Engineering and Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, College of Civil Engineering, Tongji University, Shanghai, SH 200092, China;3. Department of Geotechnical Engineering and Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, College of Civil Engineering, Tongji University, Shanghai, SH 200092, China;1. COWI UK, London, UK;2. Civil and Environmental Engineering Department, Universiti Teknologi Petronas, Perak, Malaysia;3. Department of Mining, Faculty of Engineering, Urmia University, Urmia, Iran;1. School of Construction and Environmental Engineering, Shenzhen Polytechnic, No. 7098, Liuxian Avenue, Nanshan District, Shenzhen, Guangdong Province, China;2. Key Laboratory of Geomechanics and Embankment Engineering of the Ministry of Education, Geotechnical Research Institute, Hohai University, 1 Xikang Road, Nanjing 210024, China;3. Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China;4. College of Mechanics and Materials, Hohai University, Nanjing 210024, China;1. Department of Civil Engineering, Quaid-e-Awam University of Engineering, Science & Technology, Sindh, Pakistan;2. College of Civil and Transportation Engineering, Shenzhen University, Shenzhen, China;3. Department of Civil Engineering, Mehran University of Engineering & Technology, Shaheed Zulfiqar Ali Bhutto Campus, Khairpur Mirs, Pakistan |
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| Abstract: | Three-dimensional (3D) finite element analyses have been performed to study the behaviour of a single pile and 3 × 3 and 5 × 5 pile groups during open face tunnelling in stiff clay. Several governing factors, such as tunnelling-induced ground and pile settlement, axial pile force changes and shear transfer mechanism at the pile–soil interface, have been studied in detail. Tunnelling resulted in the development of pile head settlement larger than the free-field soil surface settlement. In addition, axial force distributions along the pile change substantially due to changes in the shear transfer between the pile and the soil next to the pile, which triggers tunnelling-induced tensile forces in the piles with tunnel advancement. It was found that the relative displacements and the normal stresses at the pile–soil interface drastically affected shear transfer. The extent of slip length along a pile increased as the tunnelling proceeded. The apparent allowable pile capacity was reduced by up to approximately 42% due to the development of tunnelling-induced pile head settlement. Shear stress on the pile was increased for most of the pile depth with tunnel advancement, which was associated with changes in soil stresses and ground deformation, and hence, the axial pile force was gradually reduced with tunnel advancement, indicating the development of tunnelling-induced tensile pile force. The maximum tunnelling-induced tensile force on the pile was approximately 0.33Pa, where Pa is the allowable pile capacity applied to the pile head prior to tunnel excavation. The range affected by tunnelling in the longitudinal direction may be identified as approximately ?2D ～ +(1.5–2.0D), where D is the tunnel diameter, from the pile centre (behind and ahead of the pile axis), in terms of pile settlement and axial pile force changes based on the analysis conditions assumed in the current study. Larger pile head settlements and smaller changes in axial pile forces were computed for piles that were part of groups. It has been found that the serviceability of piles experiencing adjacent tunnelling is more affected by pile settlement than by axial pile force changes, in particular for piles inside groups. The magnitude of the tunnelling-induced excess pore pressure was small and may not substantially affect pile behaviour. |
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| Keywords: | Numerical modelling and analysis Open face tunnelling Piles Soil–structure interaction Shear transfer Stiff clay |
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