Abstract:

In order to enhance the application of double-row inclined-vertical pile composite support in loess foundation pits, model tests were conducted to investigate the displacement, internal force, and earth pressure changes of forward-inclined rear-vertical double-row piles and double-row inward-inclined pile support structures during excavation. Numerical analysis was also used to explore the effect of pile inclination on support performance. The results show that the horizontal displacement of the pile body and surface settlement outside the pit are both smaller in the inward-inclined double-row pile support compared to the forward-inclined rear-vertical pile support. Additionally, the maximum axial force, bending moment, and net earth pressure on the front row piles are also lower. As the pile inclination increases, the pile top displacement, surface settlement outside the pit, and the maximum axial force of the pile body decrease, while the maximum bending moment and the safety factor of the foundation pit increase. In the double-row inclined-vertical pile support structure, the front inclined piles function to brace internally, retain the soil, and enhance structural safety and stability, whereas the rear vertical piles serve to anchor, transfer, and distribute earth pressure. Together, they improve the overall stability of the support system. During excavation, the stress path of the soil outside the pit initially moves away from and then approaches the failure K_f line. A greater pile inclination results in the stress path staying further from the K_f line. Comparatively, the stress path of the inward-inclined double-row pile support stays further from the principal stress K_f line, leading to higher safety and stability of the foundation pit.

Key words: double-row inclined-vertical piles, forward-inclined rear-vertical double-row piles, support performance, stability, model test, numerical simulation