Experimental Study on the Streaming Potential Phenomenon Response to Compactness and Salinity in Soil–Rock Mixture

Xin Zhang,Mingjie Zhao,Kui Wang

doi:10.3390/w13152071

Abstract

The study on the effect of material structure and solution properties on the streaming potential of the soil–rock mixture (SRM) will be beneficial for improving the reliability of the measurement results for self-potential monitoring in embankment dams. We design two experimental groups and investigate the changes of potential and pressure during seepage of SRM (slightly clay materials) with different compactness and different concentration. The effects of the compaction degree and solution concentration on the streaming potential coupling coefficient and streaming potential were analyzed. The test results demonstrate that when the clay content in soil matrix is slight, the potential has a linear relationship with the hydraulic head difference, and seepage obeys Darcy’s law. The surface conductivity is negligible at 0.01 M (1 M corresponds to a concentration of 58.4 g L−1) salinity, the compactness of the SRM decreases (the permeability coefficient increases), the apparent streaming potential coupling coefficient and pressure difference decrease is the reason streaming potential decreases. The permeability coefficient of the SRM is not affected by the change in salinity (0.0001–1 M) at 85% compactness, and its seepage characteristics are related to the mineral composition, morphology and the thickness of the bound water layer (electric double layer). This study lays a foundation for further research on the self-potential method to monitor the structure of embankment dams.

Highlights

The charged porous media materials in contact with water form a double electric layer at the solid–liquid interface
Owing to the substantial size difference between soil and rock, uneven spatial distribution, and clear differences in mechanical properties, it is difficult to study the seepage mechanism of the soil–rock mixture (SRM) [2,3]
The streaming potential has a linear relationship with the hydraulic head difference, and the flow of SRM follows Darcy law

Summary

Introduction

The charged porous media materials in contact with water form a double electric layer (stern layer and diffusion layer) at the solid–liquid interface. There have been several studies on the streaming potential phenomenon of rock and soil; studies on the streaming potential of soil–rock mixture (SRM) as a type of composite porous medium material are still lacking. Owing to the substantial size difference between soil and rock, uneven spatial distribution, and clear differences in mechanical properties, it is difficult to study the seepage mechanism of the SRM [2,3]. The SRM is often used as a filling material for dams. As the main engineering characteristics of SRMs, have always been the focus of dam safety monitoring

Methods

Results

Discussion

Conclusion