Settlement And Stability Analysis Of Bridge Piles Foundation In String-beaded Karst

With the continuous development of infrastructure, more and more engineering projects were inevitably constructed in karst region. Many researches about the influence of the stability of carst on pile foundation have been carried out, but these works considered only single cavity. In fact, pile founations often have to cross several cavities in developing carst area, but few studies accounted for the load-bearing characteristics of this kind of piles. And current related codes about pile foundation design have also failed to provide effective calculation and design methods accrodingly. Therefore, to find out the load-bearing deformation, settlement calculation and stability analysis methods of piles that crossed several cavities has important theoretical and practical significance to improve the design theory and its application for pile foundations in carst region.To this end, the characteristics of the shaft resistance and toe resistance of pile installed in string-beaded carst, the load-bearing property, and the character of strata were incorperated to investigate three ideal failure models of rock with cracks:separation destroy, compression destroy and shearing destroy, and three unstability characters of carst:punching failure, shearing failure and flexing failure.With regards to the characteristics of piles passing through caves and layered subsoil, the impact of the filling in cave was not considerd, and load-transfer model proposed by Sato Satoru was introduced to simulate the development of side friction and tip resistance of the pile. Then, based on the discontinuity of derivatives, formulas to calculate the settlement along the pile length was derived for three vaious bearing cases (i.e., the bearing state of the suboil surrounding the pile shaft is elastic, partial plastic, and fully plastic, respectively). Finally, the presented technique in this paer was applied to an engineering example, of which the result showed a good agreement with the measured data and verified the applicability.In the end, based on the finite difference software FLAC3D, a simplified numerical analysis model simulating a single pile passing through multiple caves was established. Then, parametric analysis was conducted to explore the influencing rules by the existence of cave, cave quantity and distribution, cave geometry (radius and height), which can be used to provide reference for similar engineering cases in practice.