Seepage Erosion and Stability Criterion for Construction and Demolition Waste Particles in Embankment Fill Applications

Constructing highway embankment is an efficient way for large-scale utilization of construction and demolition waste (CDW). This study evaluates the seepage erosion behavior of compacted CDW particles through seepage tests on continuously and gap-graded specimens with varying fines contents under constant and cyclic hydraulic gradients. Erosion behavior was analyzed, including changes in fine particle loss, fines content, and permeability. Results demonstrate that CDW particles compacted at a required porosity of 25% or less generally exhibit seepage stability. The optimal fines content among the examined levels is approximately 35%, at which the fine particle loss remains below 0.55% for continuously graded specimens under constant hydraulic gradients. For the gap-graded specimens, particularly those lacking 1.0–2.0 mm particles, the fine particle loss increases to 2.63%. Cyclic hydraulic gradients increase the total fine particle loss by 1.16%–2.45% and fines content variation in each layer by 0.53%–1.61% compared to constant gradients. An internal stability criterion that characterizes the fine particle migration and the difference between various soil layers was proposed, providing a reliable tool for assessing the internal stability of CDW particles.