Effect of pore water chemistry on anisotropic behavior of clayey soil and possible application in underground construction

The effect of pore water chemistry on anisotropic behavior of consolidation and shear strength of reconstituted Ariake clay has been investigated experimentally. Two types of chemicals added into the pore water of the soil for enhancing flocculation microstructure of soil particles are sodium chloride (salt) (NaCl), and calcium chloride (CaCl2); and two dispersants added are sodium triphosphate (Na5P3O10) and sodium hexametaphosphate (Na6P6O18), respectively. The concentrations of these chemicals in pore water were 2-3%. Degrees of anisotropy of the coefficient of consolidation and undrained shear strength decreased with adding NaCl and CaCl2, but increased with adding the dispersants. Degree of anisotropy also increased with one-dimensional (1D) deformation and the samples with dispersive additives had higher increase rate. It has been confirmed qualitatively by scanning electron microscopy (SEM) images that adding dispersive chemicals promoted the formation of dispersive microstructure and increased the degree of anisotropy, and the chemicals enhancing flocculent microstructure had an inverse effect. The possible application of the findings to underground construction has been discussed also.