Experimental Study on Multiscale Engineering Properties of EICP Combined with Xanthan Gum Solidified Sand

In this study, enzyme-induced carbonate precipitation (EICP) combined with xanthan gum curing technology was used to improve the engineering properties of standard sand, and the curing effect of EICP combined with different xanthan gum contents was studied by macroscopic tests such as unconfined compressive strength, direct shear, permeability, calcium carbonate content, and microscopic tests such as scanning electron microscope and nuclear magnetic resonance. The results show that the unconfined compressive strength, shear strength, cohesion and internal friction angle of EICP combined with xanthan gum solidified sand increases with the increase of xanthan gum content and reaches the maximum value at the content of 2%, in which the increase of unconfined compressive strength, shear strength, and cohesion is significant; further, the increase of internal friction angle is small. The permeability coefficient of EICP combined with xanthan gum solidified sand decreases with the increase of xanthan gum content, and the permeability coefficient of 2% xanthan gum is only 65.4% that of pure EICP treatment. The incorporation of xanthan gum promotes the deposition of calcium carbonate, increases the viscosity of the reaction solution, and produces colloidal encapsulation and bonding effect on the sand particles. In addition, the incorporation of xanthan gum effectively reduces the porosity of solidified sand and greatly reduces the proportion of large pores and medium pores by changing the pore size, which greatly improves the pore structure.