Abstract
The embankment slope is vulnerable to slip and collapse, when prestressed concrete pipe (PCP) piles are used to reinforce the inclined soft foundation to bear the load of the embankment. Accordingly, this study puts forward new programs for strengthening embankment foundation with inclined, rather than vertical, PCP piles. Based on an actual engineering accident with embankment slope collapse, this study establishes a finite element model, accompanied by analysis of engineering characteristics and reinforcement effects of the foundation. The main conclusions are drawn as follows: (1) when a pile‐supported foundation is used to strengthen the inclined soft foundation, PCP piles in the lower part of the embankment are subjected to bending moments, with their maximum value appearing in the upper part of the PCP pile at the embankment slope foot. During the embankment filling, the maximum pile bending moment may reach the ultimate bending load, resulting in bending failure accompanied with large lateral displacement and even slope collapse. The maximum horizontal displacement of the foundation is located at the foot of the embankment slope. (2) Reinforcement using inclined PCP piles contributes to smaller maximum pile body bending moments than that using vertical PCP piles and loading berms, and such contribution is enhanced when the inclination angle of PCP piles in the lower part of the slope gets larger. Therefore, inclined PCP piles with high angles are optimum in improving the overall stability of the foundation. (3) Compared with vertical PCP piles, inclined PCP piles contribute to smaller horizontal displacement and vertical settlement in foundation reinforcement, which means better reinforcement effects. Moreover, as the inclination angle of PCP piles increases, the maximum displacement decreases rapidly, associated with greatly enhanced lateral stability.
Highlights
When filling high embankments on an inclined soft foundation, reinforcement is significantly necessary due to insufficient foundation-bearing capacity
(2) Reinforcement using inclined prestressed concrete pipe (PCP) piles contributes to smaller maximum pile body bending moments than that using vertical PCP piles and loading berms, and such contribution is enhanced when the inclination angle of PCP piles in the lower part of the slope gets larger. erefore, inclined PCP piles with high angles are optimum in improving the overall stability of the foundation
Horizontal displacement is mainly concentrated in the slope, and it decreases in the direction away from the embankment foot, reaching the maximum at the slope foot
Summary
When filling high embankments on an inclined soft foundation, reinforcement is significantly necessary due to insufficient foundation-bearing capacity. Rigid piles at different locations present different stability controls on the embankment Those in the middle-lower part of the embankment mainly bear the vertical load of the upper embankment, which means they are primarily in the compression zone (Figure 1). The loading berm (Figure 2(a)) has been commonly used at the outside part of the embankment slope in practical engineering to increase the overall stability Such a loading berm can enhance the sliding thrust of the foundation to a certain extent when it is used on the inclined soft foundation. Since inclined PCP piles in the bending-shear zone are subjected to both vertical loads from the upper embankment and horizontal loads, it is challenging to well understand their mechanical characteristics and reinforcement effects. Results of this study are expected to provide a reference for engineering application of this new soft foundation reinforcement program
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