Effect of Clay on Internal Erosion of Clay-Sand-Gravel Mixture

Chen Liang,Chen Cheng,Cai Guo-Dong,Gu Jia-Hui,Yefei Tan ,Zi-Xue Yin

doi:10.1155/2020/8869289

Abstract

In this study, a one-dimensional seepage test apparatus was used to investigate the effect of clay on the critical hydraulic gradient, hydraulic conductivity, migration of fine particles in soil, and percentage of fine particle loss during the internal erosion of clay-sand-gravel mixture, compared with clean gravel. The critical hydraulic gradient and fine sand loss percentage of the clay-sand-gravel mixture decreased, and critical flow velocity and the hydraulic conductivity increased. Six clay-sand-gravel mixture samples with different clay contents were used to evaluate the effect of different clay contents on internal erosion. As the percentage of clay mass to fine particle mass increases from 0% to 25%, the critical hydraulic gradient of soil samples decreases by nearly half and the fine sand loss percentage decreases from 13.73% to 3.48%. Overall, clay has a significant effect on the development of internal erosion of clay-sand-gravel mixture. And attention should be paid in engineering project; clay-sand-gravel mixture with a small amount of clay is more likely to be damaged than clean gravel.

Highlights

China has 14,500 km of seawall, but the length conforming to standards is only 6181.8 km
“Internal erosion” usually includes “suffusion” and “piping.” During the suffusion process, fine particles are eroded by seepage through the pores between the larger particles, leaving the coarse framework, while piping is like gradual erosion and transportation of fine particles along the flow path
During the seepage failure stage, the critical hydraulic gradient of each sample in the CS group generally decreased as the clay content increased, and the critical flow velocity for failure increased with the clay content

Summary

Introduction

China has 14,500 km of seawall, but the length conforming to standards is only 6181.8 km. Several studies have been conducted to investigate the mechanical behavior of soils subjected to internal erosion by controlling the hydraulic gradient to simulate the erosion process [16,17,18,19]. Little research has been done about the effect of clay on fine sand loss and critical hydraulic gradient due to internal erosion of gravel sand-clay mixtures, which is of great significance for engineering construction and risk assessment. In construction projects, such as the reclamation of embankments, sand-gravel mixtures often contain a small clay amount, so it is important to investigate the effect of clay on internal erosion of clay-sand-gravel mixtures

Materials and Test Apparatus

Testing Procedure

Results and Discussion

Conclusions