Precast prestressed high-strength concrete (PHC) pipe pile with cement-improved soil is a novel pile foundation technique that has been extensively utilized in contemporary years due to the enhanced lateral load-bearing capacity in soft grounds. However, though several studies have shown the damage mechanism of single piles with cement-improved soil, the group behavior of such pile foundations is still largely unexplored. Hence, this article aims to illustrate the lateral capacity and tension-induced failure characteristics of single and 1 x 2 group PHC piles reinforced by cement-improved soil. Extensive 3D nonlinear finite element analyses have been performed and the precision of the numerical models is confirmed by a previous experimental-numerical study. The effects of pile spacing, embedment length, and cement-improved soil thickness were examined in terms of various lateral responses and damages. Results have revealed that the addition and thickening of CIS around core piles enhances the overall pile performance and protects the core pile from excessive tensile damage. Declines in head displacement and bending moment were found to be up to 45 % and 25 % for single piles, and up to 47 % and 24 % for group piles, respectively. Moreover, the presence of CIS makes the stress distribution mechanism between the trailing and leading piles in group arrangement more uniform. Results of this study are expected to provide valuable insights for a better understanding of the damage behavior of group precast piles reinforced with cement-improved soil.

This study investigates the effects of adjacent deep excavation on the seismic performance of buildings. For that purpose, the numerical models are constructed for different buildings (i.e., 5-Story building and 15-Story building) considering the deep excavation-soil-structure interaction (ESSI) and soil-structure interaction (SSI). The results achieved from the ESSI and SSI systems are discussed and compared. Fully nonlinear numerical models with material, geometric, and contact nonlinearities are developed. Eleven earthquakes with different intensities, epicentral distances, significant durations, and frequency contents are applied to the models; and, the numerical results are given in terms of average records. The buildings are carefully designed and verified based on common design codes. The numerical modelling procedure of the deep excavation-soil system is validated using centrifuge test data. The comparisons between the ESSI and SSI systems are carried out in terms of accelerations, lateral displacements, inter-story drifts, story shear forces, and the nonlinear behavior of the soil medium under the buildings. The results show that it is necessary to consider the ESSI effect, and it might significantly change the seismic behavior of buildings adjacent to the deep excavations. The findings from this study can provide valuable recommendations for engineers to design buildings close to deep excavations under earthquakes.