Experimental Study On Dynamic Characteristics Of Microbial Modified Soil

Microbial inducing the crystallization of calcium carbonate,also known as MICP which is a new technology to deal with the liquefaction of sand.This technology can improve the liquefaction resistance force by delivering the microbial liquid and nutrient fluid into the fixed sand ground(a mixture of urea and CaCl2),which will bring the crystallization of calcium carbonate gel in the sand pores between grains.The technology of microbial soil microorganism can be put into practice by grouting,and the advantages are:grouting reinforcement effect is obvious,simple technique,low perfusion pressure,transmission distance,small disturbance,short duration,and low power consumption.This is a cutting-edge technology of the reinforcement of liquefiable foundation research.This paper is mainly to verify the effect of technology to improve the liquefaction resistance of foundation soil reinforcement grouting and grouting for microbial microorganisms through the indoor dynamic three axis and resonant column test.Also,the comparison was made among different reinforcement schemes.Steps are listed as following:(1)Introduce technical principles and methods of microbial grouting reinforcement of soil with some literature reviews,and provide practical methods of microbial grouting which can be used to reinforce liquefied sand subgrades.(2)Confirm and purchase microorganisms and substrates,what's more activate microbial freeze dried powder after purchase.(3)To make a plan,analysis grouting sample by using dynamic triaxial test which were completed by grouting reinforcement.To study the dynamic characteristics of the sample,especially the liquefaction resistance.The scheme is mainly:the control of different test conditions,explore the reinforcement effect of different relative densities of reinforcement for sand relative density;analysis on the anti liquefaction properties of grouting reinforcement in different sample time,the time required to make test plan for reinforcement;concentration of different bacteria and different interest rates,the optimization scheme of perfusion etc..Based on the calculation model and empirical formula,the pore water pressure development law of grouting reinforcement is studied.(4)Indoor resonant column test based on MICP parameters of grouting reinforcement specimens,shear modulus and damping ratio under different test specimen,the grouting reinforcement effect on reinforced specimens from another aspect and anti liquefaction ability.Furthermore,the optimal relative density,the grouting time and the optimization of grouting reinforcement are determined.?Based on the research of MICP microbial grouting reinforcement technology,the feasibility of the modified soil was verified,which made the amount of grouting liquid and the grouting batch greatly reduced,and the curing time decreased to 10h.Through the optimization of the perfusion scheme,the uneven distribution of CaCO3 gel was slow down and the curing strength was maximized.It is an important step for the application of this technology in practical engineering.