Experimental study and mechanism analysis on sand reinforcement with different compositions of biological solution

Abstract:

To assess the possibility of promotion of fresh medium to resuspend thallus (RF) in sand reinforcement and its mechanisms, a series of solution and sand column tests were conducted to analyze the abilities of four biological solutions with different compositions in urea hydrolysis, MICP, and sand reinforcement. Results show that the ability of the original bacterial solution (US) without any treatment after the completion of culture in urea hydrolysis and MICP mainly derived from the urease in thallus, and the other part came from the free urease released by lysis of bacteria. With high concentration of bacterial solution, the resuspension of thallus by fresh medium could promote the MICP ability of thallus of the biological solution to some extent, however, the removal of supernate (SS) in preparing RF led to urease loss, which resulted in the total MICP ability of RF basically the same with that of the original bacterial solution. The sand column reinforced by original bacterial solution had more calcium carbonate precipitation and higher shear strength, and the co-existence of SS and thallus led to more effective cementation contact. Compared with RF, US has the characteristics of simple, low cost, and high activity, which can be preferred selected in the application of MICP in solving the foundation problem that requires rapid reinforcement.