Experimental Study On Mechanical Properties Of Artificial Bonded Sand Based On MICP Method

Most of the traditional chemical grouting materials and chemical curing agents contain toxic chemicals.In the process of engineering construction,the use of it will increase the degree of environmental pollution,so it is of great practical significance to study the new type of environmentally friendly soil reinforcement technology.Microbial induced calcium carbonate precipitation,as a kind of bio-mineralization in nature,has many advantages such as simple mechanism,high efficiency,easy control and good environmental tolerance.The application of this technology to soil consolidation will bring great environmental benefits and economic benefits.Based on the MICP method,this paper mainly used Sporosarcina pasteurii for the solidification of standard cement.Based on the MICP method,the experiment of microbial activation,culture and preservation were carried out.At the same time,X diffraction,scanning electron microscopy,consolidated drained shear,unconfined compression and calcium carbonate content were studied.The effects of the concentration of nutrient solution,the treatment method and the culture temperature on the physical and mechanical properties of MICP cemented specimens were studied.This paper provides basic data for the practical application of MICP solidified soil.The main research results are as follows:(1)The change of nutrient solution concentration has a great influence on the physical and mechanical properties of the soil.Under the same amount of nutrient solution and reaction time,with the increased of the concentration of the nutrient solution,the strength of the cemented sample increased first and then decreased.(2)MICP cement samples showed consolidation drained shear stress softening form,test results show that the deposition of calcium carbonate on the sand has inhibitory effect of shear dilation.At the same time,the elastic modulus increases with the increase of the dry density of MICP cemented specimens(3)In the experiment of nutrient solution concentration,the bond strength and internal friction angle of 0.5M cemented specimens were the largest,and the cementation effect was the best.Based on the experimental results and previous studies,it is concluded that 0.5M cemented specimens have good distribution of calcium carbonate and high content of calcium carbonate.(4)The combination of high and low concentration of nutrient solution was used to cement standard sand.In the short time,the cement sample can show higher strength,calcium carbonate content and better uniformity,It is suitable for the soil with low cementation depth and high strength,this method has good engineering application potential.(5)The effect of culture temperature on the test results showed : when the cemented specimens were cultured at the temperature of 20,30 or 40,the content of calcium carbonate changed little,but the change of temperature had obvious influenceon the strength and deformation modulus of the samples.With the increase of temperature(20-40 ℃),the strength and deformation modulus of the samples were increased first and then decreased.Based on the analysis of test results,the reason of this appearance is that due to the different temperature,the precipitated calcium carbonate is different.