Experimental Study On Strengthening Calcareous Sand With Different Enzyme Sources In Seawater Environment

Microbiological induced deposition of calcium carbonate（MICP）has been widely used in soil reinforcement because of its high efficiency and environmental protection.It is through the use of urease metabolism produced by microorganisms,the nutrient in the environment will induce the formation of calcium carbonate deposition in the sand,so as to strengthen the sand.But given the bacterial activity more difficult to control,bacteria,as large as the present situation of the uneven and solid,and inadequate strength,some scholars proposed the enzyme to induce deposition of calcium carbonate（EICP）and soybean urease induced calcium carbonate precipitation（SICP）,they are the direct use of small molecules of urease instead of microbial urease,and solid is relatively uniform,And the strengthening strength has been effectively improved.In this paper,the change law of urease activity from different sources of MICP,EICP and SICP with time was explored.The influencing factors of MICP reaction and reaction mechanism in seawater environment were analyzed by aqueous solution test,and the optimal concentration of CATALYST for EICP and SICP were also analyzed.Finally,five different methods based on three technologies were adopted.In other words,urease was purified by bacterial fluid,urease was purified by bacterial fluid with skim milk powder,urease was purified by soybean,and urease was purified by soybean with xanthan gum.The main conclusions were as follows:（1）The overall change trend of different ureases with time in the 17 days,with the highest activity in the first 2 days,and then gradually decreased,and different ureases have different adaptability to low temperature（4℃）and room temperature（25℃）,and the overall intensity of each urease is obviously different.（2）According to the SEM,EDS and XRD test results of MICP aqueous solution test,the MICP reaction in seawater environment is more introduced than the reaction process in deionized water environment.Mg²⁺,Ba²⁺and CO₃^2-and OH^-bond to form Mg₅（CO₃）₄（OH）₂·4H₂O and Ba CO₃crystals.The EICP and SICP aqueous solution tests determined that the concentration of 10 g/L and soybean bean powder was 130g/L.（3）The compressive strength,calcium carbonate content and SEM were tested by MICP,EICP,EICP and SICP technology.The results showed that EICP and SICP were uniform compared with MICP and solids,and the rupture effect of the EICP/SICP and SICP technology was significantly higher than that of MICP.