| Ecological management in desert area is very important for sustainable development of human society.Microbial mineralization(MICP)technology shows the characteristics of rocksoil matrix affinity and environmental friendliness,it has become a new technical means in ecological control of desertification.In the application of the technology of sand consolidation by microbial mineralization in desert areas,the influence of external environmental factors such as diurnal temperature difference and strong evaporation is also involved,besides the influence of materials and temperature under normal laboratory conditions,these problems are very important for the successful application of microbial mineralization sand consolidation technology from laboratory to field.The purpose of this paper is to study the influence factors and their changing rules of microbial sand consolidation under the conditions of temperature change and evaporation,the influence of temperature field and radiation temperature variation on the process of microbial mineralization was analyzed by simulating evaporation characteristics of desert climate and controlling radiation heat source.Finally,the matrix suction and cumulative evaporation rate were measured under different calcium carbonate distributions,and the interaction among unsaturated,evaporation and MICP was analyzed.The main research contents and results of this paper are as follows:(1)The experiment of microbial mineralization in solution was carried out in the temperature range of 30℃～50℃.The results showed that the activity of urease increased exponentially with the increase of temperature.The p H value and the conversion rate of calcium ion were negatively correlated with the concentration of cementing solution.When the temperature rises to 50℃ and the concentration is 1.25mol/L,the microbial mineralization is strongly inhibited and the calcium carbonate production is greatly reduced.(2)In the experiment of sand consolidation by surface infiltration without heat source radiation,the total calcium carbonate formation rate of the samples was positively correlated with the concentration and infiltration amount of the cementing solution,and the total calcium ion conversion rate of the samples was negatively correlated with the concentration and infiltration amount of the cementing solution The correlation between the formation rate of shallow calcium carbonate and the initial water content of shallow layer is poor,while the formation rate of deep layer calcium carbonate is highly consistent with the initial water content of deep layer,and the distribution law of calcium carbonate decreases gradually from top to bottom.(3)In the sand consolidation experiment of simulated solar evaporation surface infiltration,the process of microbial mineralization in the shallow layer(0～2cm)was inhibited at low infiltration rate,and with the increase of infiltration rate,the process of microbial mineralization in the shallow layer(0～2cm)was promoted,the distribution of calcium carbonate increases first and then decreases with the depth increasing,reaching a peak at the shallow sand layer,and the MICP process in the shallow layer of the sample with the concentration of 1.25mol/L cementation solution is obviously inhibited,the formation rate of shallow calcium carbonate is lower than the concentration of cementing solution of 1.00mol/L.At the same infiltration rate and concentration of cementation solution,the overall calcium carbonate formation rate of the sample irradiated by no heat source was higher than that of the sample evaporated by sunlight,but the calcium carbonate formation rate of the sample evaporated by sunlight in the shallow layer(0～2cm)was higher than that of the sample irradiated by no heat source.(4)In 25℃ evaporation environment,when the formation rate of calcium carbonate in surface layer is higher than that in shallow layer,the cumulative evaporation rate is positively correlated with the formation rate of calcium carbonate,and the formation of calcium carbonate promotes water evaporation;When the formation rate of calcium carbonate in the surface layer is lower than that in the shallow layer,the cumulative evaporation rate is negatively correlated with the formation rate of calcium carbonate.In the 40℃ evaporation environment,the cumulative evaporation rate was positively correlated with the formation rate of calcium carbonate under both distributions,and the resistance to evaporation was better when the formation rate of calcium carbonate was more distributed in the range of 0～2 cm.(5)Under the same water content,the formation rate of calcium carbonate has a positive correlation with the suction of sand matrix,and the lower the water content,the more the suction of sand matrix increases Under the same water content,the matrix suction of the surface sand is greater than that of the shallow sand,which promotes the water migration from bottom to top Under the same water content,the matrix suction of the surface sand is lower than that of the shallow sand,which hinders the water migration from bottom to top. |
