ABSTRACT
Basement construction and deep excavation in very soft clay could induce excessive ground movements and cause adverse effects on piles located inside the excavation area. The research was conducted using data from field monitoring on the instrumented pile inside the basement and three-dimensional numerical back-analysis to evaluate the pile-soil interaction under various basement construction techniques. The key factors investigated in this study include the influence of the basement construction method, system stiffness, pile-soil stiffness, and duration of construction period. Moreover, the influence of soil consolidation, pore pressure dissipation, and time-dependent soil behaviour on pile response is thoroughly investigated. Field measurements are conducted at selected construction sites in Bangkok, where retaining structures include jet-grouted retaining walls and cut-slope excavation. The diameter bored pile ranges from 0.6 m to 1.5 m and the depth of the pile tip is 50 m. The fully coupled three-dimensional finite element method using a hardening soil model with small strain stiffness is utilized to simulate the complex soil-structure interaction, considering the time-dependent behavior of soft clay to provide insights into observed behavior. A series of numerical parametric studies are carried out to identify the impact of each investigated factor affecting pile movement. The key results highlight the importance of system stiffness of the retaining structure that strongly impacts pile movement inside the basement. The time-dependent behaviour can cause larger pile movement in retaining systems with smaller stiffness, such as cut-slope excavation, than those with rigid retaining walls.
