Bearing stratum effect at pile end of pile-cap-net structure subgrade based on centrifugal model tests

To investigate the effect of the strength of bearing stratum at pile end on the bearing behavior of pile-cap-net structure subgrade (foundation), four groups of centrifuge model tests, separately with different bearing stratum situations at pile end, are designed. The deformation of foundation, tensile force in reinforced cushion, and vertical compression at the bottom of embankment are recorded. The test data show that: ①with the decrease of the strength of bearing stratum at pile end, the foundation turns from stability to the status with stab deformation of pile end and then to the status with local shear failure in bearing stratum at pile end; ②with the increase of the strength of bearing stratum at pile end, the deformation of the foundation reduces. The relationship between the stab deformation of pile end under subgrade center, foundation surface settlement, average value of horizontal foundation deformation under slope toe and the bearing capacity of bearing stratum at pile end can be described as the power function; ③with the increase of the strength of bearing stratum at pile end, the bearing concentration effect of piles and the bearing attenuation effect of soil between piles become obvious; ④the relationship between the foundation surface settlement under subgrade center and the average value of tensile force in reinforced belt under subgrade surface is described as the quadratic polynomial. The calculated values of reinforced belt force considering embankment lateral sliding are relatively close to the test data; ⑤with the increase of the strength of bearing stratum at end-support friction pile end, the force in the reinforced belt decreases; ⑥the layout of sand wick can accelerate the drainage consolidation of foundation and improve the bearing capacity of bearing stratum at pile end and enhance the stability of foundation.