Different effect of sodium polyacrylate dispersant on shear strength of shield tunneling soil

Abstract

Shield Tunneling soil has large reserves and can be recycled as road material, with considerable economic and environmental value. However, the concentration of the Sodium Polyacrylate dispersant (PAANa-D) varies greatly in recycling, resulting in uncontrollable soil mechanical property. This study employed a suite of tests to analyze the impact mechanism of PAANa-D on the shear strength of Shield Tunneling clays including Ca-Montmorillonite, Kaolinite and Illite. To investigate the impact mechanism from the PAANa-D function, the sedimentation test, the zeta potential test and the rheology and transmission electron microscope test were employed to analyze the transformed mechanism of the function. In addition, according to the stabilization of PAANa flocculant gelation, the stabilized potential of PAANa-D was explored by the loss factor test, the BETP and MIP test. The results indicate that the PAANa-D decreased the shear strength. In the lower concentration, the PAANa-D increased the electrostatic repulsion, resulting in the decreasing cohesion. In the higher concentration, the PAANa-D molecules entangled into the gel-like cluster, which decreased the angle of internal friction. However, during the moisture loss, the PAANa-D also had the potential to stabilize the clays. Although the higher concentration hindered the compaction, the gelation of PAANa-D bound the particles and filled the pores. The strength increased with the moisture loss. The findings offer systematic insight into the correlation between polymer dispersant and shear strength, and proffer pragmatic recommendations for the utilization of Shield Tunneling soil as road material, thereby addressing the predicament of its uncontrollable mechanical properties.