Temporary Solidification of Coarse Grained Soil by Magnetorheological Fluids

Abstract

Magnetorheological fluids (MRFs) are suspensions of micron-sized, magnetizable particles in a base fluid such as water, oil, or silicon, that freely transition from fluid to semi-fluid to solid states when subjected to magnetic fields. The pr esent paper explores the usage of MRFs to temporarily solidify coarse -grained soils. The laboratory testing program included hydraulic conductivity tests of MRF through Ottawa 20-30 sand; bender element tests to investigate how small strain shear modulus varies with applied magnetic field strength, and direct shear tests to evaluate the strength of MRF-solidified soil. The tests revealed that solidification of a soil with MRF results in very large increases in small strain shear modulus and strength and considerable reduction in hydraulic conductivity. However, only medium to coarse sands could be permeated by the MRF as clogging of the pores occurs in finer grained materials. Practical applications for MRF -solidification and future research needs are discussed. Preface While Professor Richard Woods is certainly best known and honored for his landmark accomplishments in soil dynamics research, his interests included other geotechnical engineering topics including foundations, soil improvement, shallow geophysical testing and others. In the 1980’s Professor Woods investigated the effectiveness of partial grouting on the properties of cohesionless soils (Chang and Woods, 1992). He utilized surfactants (foams) that could create partially grouted soils whose performances approached that of fully grouted materials. En route, he was among the first to discover that surfactants could also effectively clean soils of chemical pollutants by rapidly and completely displacing all of the fluid from the soil pores (Chu and Woods, 1996). The present paper on solidification of coarse -grained soils by magnetorheological fluids is submitted in recognition of Professor Woods’ soil improvement research.