Effect of Gradation Characteristics and Particle Morphology on Internal Erosion of Sandy Gravels: A Large-Scale Experimental Study

Abstract

Internal erosion refers to the seepage-induced fine particle migration phenomenon in soil. Deep alluviums in valleys usually contain cohesionless gap-graded sandy gravels with poor internal stability. The construction of embankment dams on such alluviums could pose a high risk of internal erosion. This study systematically investigated the internal erosion of cohesionless gap-graded sandy gravels with an emphasis on the effects of gradation characteristics and particle morphology. A series of large-scale internal erosion tests were conducted on gap-graded sandy gravels with different gap ratios, fines contents, and coarse particle morphologies under the surcharge pressure of 1 MPa. The internal erosion characteristics, including soil permeability, eroded soil mass, and soil deformation during the erosion process were comparatively analyzed in combination with a meso-mechanism interpretation. The results show that the increase of the gap ratio can reduce the internal stability of soil and promote the mechanical instability. Fines content affected the permeability and internal stability of soil by altering the filling state of inter-granular pores and the constraints on fine particles. Coarse particles with higher roundness, sphericity, and smoothness can facilitate the movement of fine particles and promote the mechanical instability of the soil matrix.

Characterization of the Migration of Soil Particles in Lateritic Soils under the Effect of Rainfall

“…The stability of soil slopes is affected by erosion within the soil body, and this erosion process refers to the transport of fine particles located in the interstices of the coarse particles of the skeleton under the action of seepage. In this case, the coarse particles form the soil skeleton, while the fine particles are free to move in the coarse skeleton under the action of seepage forces [10][11][12][13]. During heavy rainfall, fine particles in the slope flow between gravels, but due to the limitation of pore size, some fine particles will gather in the slope during transportation [14]; others converge to the lower part of the slope and the toe of the slope and ultimately lead to the destruction of the slope [15][16][17].…”