Experimental visualization of soil arching evolution and collapse in pile-supported embankments under cyclic loading

Soil arching is a fundamental mechanism governing the stability of pile-supported embankments, a widely adopted solution for constructing transportation infrastructure on soft soils. However, the internal evolution and degradation of soil arching under long-term traffic-induced cyclic loading remain inadequately understood, limiting the ability to assess long-term performance. This study presents an innovative experimental framework combining transparent soil and Particle Image Velocimetry (PIV) to directly visualize and quantify the internal deformation and stress redistribution within embankment fills subjected to cyclic loading. The results, obtained from model tests with a normalized embankment height ( H / B ) ranging from 1.5 to 2.5, reveal that the stability and failure mode of soil arching are predominantly controlled by H / B . Two distinct collapse mechanisms are identified: (i) an immediate global collapse for low embankments ( H / B = 1.5 ) attributed to insufficient confining stress, and (ii) a progressive failure for higher embankments ( H / B ≥ 2.0 ), characterized by the cumulative upward migration of a shear plane. The visualized particle-scale kinematics provide some new insights into the mechanics of arching degradation under cyclic conditions. These findings advance the fundamental understanding of soil arching evolution and offer qualitative references for the performance assessment of transportation embankments within the investigated parameter range.