Composed of a raft and pipe piles with embedded heat exchange devices, a pipe-type energy piled raft foundation can enhance both foundation performance and energy utilization efficiency. An urgently needed thermomechanical analysis method would facilitate the optimization design and the broader adoption of this fundamental form. Therefore, this paper proposes an efficient method for the thermo-mechanical analysis of pipe-type energy piles with a raft in layered transversely isotropic media. The pile-soil and raft-soil interaction equations are derived by coupled finite and boundary element method. A simplified approach is then proposed and applied to tackle the pile-raft-soil coupling interaction. The correctness and efficiency of the method are verified through comparisons with a field test and two finite element numerical cases. Finally, parametric analyses are conducted to investigate the influences of temperature increment, pile thickness, raft thickness, and soil anisotropy on the performance of the pipe-type energy piled raft foundation.

This paper describes the construction of a deep basement in central London. The construction sequence for the basement was a combination of top down and blue-sky excavation to enable phased delivery of the project. Temporary single level props enabled blue-sky construction by managing ground movements. Ground movements associated with the basement construction and impact on 3rd party assets were monitored to validate the design using 3D targets and inclinometers. The ground movements were predicted at each stage of construction using simple models with more complex three-dimensional soil-structure finite element analysis used when examining the whole basement behaviour under the temporary and permanent loads. Temporary prop loads, and thermal loads on props were also monitored during the bulk digging. The small strain constitutive models for London Clay was shown to closely predict the observed movements.

Piled raft foundations are increasingly used in construction due to their cost efficiency, requiring fewer piles than traditional pile foundations. Their ability to withstand cyclic lateral loads, such as those from earthquakes and wind forces, is crucial for structural stability. Understanding their response under cyclic loading conditions is essential, and finite element modeling (FEM) is a valuable tool for analyzing these behaviors. A recent 3D FEM study examined the performance of piled raft foundations in clay soils, focusing on loading pattern, frequency, and number of cycles. Results showed that lateral load capacity decreased as cycle count and frequency increased, with full cyclic loading (FCL) having a more pronounced effect than half cyclic loading (HCL). The raft shared 20.57-39.07 % (HCL) and 27.68-55.13 % (FCL) of lateral loads at frequencies of 0.1-10 Hz over 20 cycles. Additionally, locked-in moments increased by 21 %, and the degradation factor ranged from 65 to 80 % for HCL and 70-90 % for FCL. These findings provide valuable insights into pile-soil interaction and foundation stability under cyclic lateral loading, ensuring more effective design strategies for structures exposed to dynamic forces. Future research should explore long-term cyclic effects to further optimize foundation performance.

In this study, three-dimensional numerical analysis has been performed to comprehend the time-dependent behavior of large piled rafts founded in saturated clayey soil, explicitly for the time of superstructure construction and post-construction up to the end of soil consolidation. The performance under different construction times for the corresponding unpiled raft and the piled raft with uniform pile length configuration of varying pile number, spacing, and length have been examined and then compared with that of non-uniform length configuration for the same total pile length. The dissipation of excess pore water pressure, average settlement, and differential settlement are presented and discussed in detail. A quicker dissipation rate of excess pore pressure is noted with either fewer piles, wider pile spacing, or shorter-length piles. An increase in construction time results in a lesser total average settlement at the end of consolidation. The piled raft with uniform pile length configuration shows a higher differential settlement than the unpiled raft. However, by adopting a suitable nonuniform length configuration, negligible differential settlement, higher load-carrying capacity, and a significant reduction in pile material volume can be achieved. Predictive expressions have been proposed to estimate the average and differential settlements of piled raft with uniform length configuration.

This paper aims to analyze and describe the geotechnical behavior of a piled raft foundation of a tall building (53 floors, 172.4 m high) through the monitoring of strains in the building's columns and piles, the stresses at the raft-soil interface, and the foundation settlements. Field and laboratory tests were performed, and associated with axisymmetric and three-dimensional finite element analysis to the assessment of the measured data. The monitoring of the pile strains suggests the occurrence of soil expansion, caused by the raft excavation process, up to approximately 6 months after the excavation was completed. The presence of different soil profiles under the raft, with different mechanical properties, affected the distribution of the foundation settlements and the pile loads. Initially, the average pile loads were concentrated in the perimeter elements, but, as the construction of the building evolved, they tended to become more uniform. The effect of the superstructure stiff-ness caused successive load redistributions in the columns, which contributed to the maintenance of the maximum angular distortion of the building within the allowable values and reduced the load difference between the piles positioned in opposite soil profiles.