Experimental study on degradation of EICP and xanthan gum treated calcareous silt under wetting-drying cycles

The biopolymer (BP) has been an emerging environment-friendly biomaterial for soil reinforcement in recent years. However, due to its water solubility, the strength of the BP-stabilized soil gradually deteriorates under cyclic wetting-drying conditions. Therefore, it is very important to improve the water resistance of the BP-strengthened soil. In this study, the calcareous silt in the South China Sea was reinforced by the plant urease-induced calcium carbonate precipitation (EICP) combined with the xanthan gum (XG). A series of physical, mechanical and microscopic tests are carried out on the samples under different wetting-drying cycles. The test results show that with the increase of the XG content and plant urease concentration, the unconfined compressive strength of the XG-stabilized soil and XG-EICP-stabilized soil increases significantly. With the increase of the wetting-drying cycles, the strength decrease of XG-stabilized soil is greater than that of the joint-stabilized soil, and the joint-stabilized soil has better resistance to the wetting-drying cycles. The results of the EICP and XG-EICP solution tests show that the XG can form a water-insoluble gel-like precipitate in the EICP solution, and the calcium carbonate particles attached to the XG-EICP precipitate are larger than those produced by the pure EICP. The tests verify the feasibility of the EICP to improve the erosion resistance of the biopolymer-solidified soils against the wetting-drying cycles, and it is expected to provide new ideas and methods for marine soil reinforcement.