In most coastal and estuarine areas,tides easily cause surface erosion and even slope failure,resulting in severe land losses,deterioration of coastal infrastructure,and increased floods.The bio-cementation technique ...In most coastal and estuarine areas,tides easily cause surface erosion and even slope failure,resulting in severe land losses,deterioration of coastal infrastructure,and increased floods.The bio-cementation technique has been previously demonstrated to effectively improve the erosion resistance of slopes.Seawater contains magnesium ions(Mg^(2+))with a higher concentration than calcium ions(Ca^(2+));therefore,Mg^(2+)and Ca^(2+)were used together for bio-cementation in this study at various Mg^(2+)/Ca^(2+)ratios as the microbially induced magnesium and calcium precipitation(MIMCP)treatment.Slope angles,surface strengths,precipitation contents,major phases,and microscopic characteristics of precipitation were used to evaluate the treatment effects.Results showed that the MIMCP treatment markedly enhanced the erosion resistance of slopes.Decreased Mg^(2+)/Ca^(2+)ratios resulted in a smaller change in angles and fewer soil losses,especially the Mg^(2+)concentration below 0.2 M.The decreased Mg^(2+)/Ca^(2+)ratio achieved increased precipitation contents,which contributed to better erosion resistance and higher surface strengths.Additionally,the production of aragonite would benefit from elevated Mg^(2+)concentrations and a higher Ca^(2+)concentration led to more nesquehonite in magnesium precipitation crystals.The slopes with an initial angle of 53°had worse erosion resistance than the slopes with an initial angle of 35°,but the Mg^(2+)/Ca^(2+)ratios of 0.2:0.8,0.1:0.9,and 0:1.0 were effective for both slope stabilization and erosion mitigation to a great extent.The results are of great significance for the application of MIMCP to improve erosion resistance of foreshore slopes and the MIMCP technique has promising application potential in marine engineering.展开更多
Enzyme-induced carbonate precipitation (EICP) is an emerging technique to improve the soil and most studies are carried out at room temperature. However, considering some foundations are in high-temperature environmen...Enzyme-induced carbonate precipitation (EICP) is an emerging technique to improve the soil and most studies are carried out at room temperature. However, considering some foundations are in high-temperature environments (>40 ℃), the higher urease activity at high temperature results in the solidification inhomogeneity, limiting the application of EICP. The higher urease activity at high temperature hampers the application of EICP because of solidification inhomogeneity. The garlic extract has been used as a type of urease inhibitor in medical science and food engineering. Here, we propose to use it to control urease activity for sand solidification at high temperature. The effects of garlic extract addition on urease activity and precipitation rates for calcium carbonate (CaCO_(3)) were studied. Extra tests were conducted to study the effect of garlic extract addition on the solidification homogeneity. The results showed that the garlic extract addition significantly decreased urease activity. To reduce the rate of CaCO3 precipitation at different temperatures, a suitable concentration of garlic extract was necessary to obtain a suitable urease activity. In the sand solidification test, garlic extract addition resulted in a smaller difference in sonic time values or CaCO_(3) contents at different parts of samples. The improved solidification homogeneity can achieve higher strength. The correlation between sonic time values and CaCO_(3) content was higher than that between CaCO3 content and strength. Appropriate concentrations of garlic extract were obtained at 35 ℃, 40℃, 45 ℃, 50 ℃, and 55 ℃. The proposed garlic extract addition method was significant to improve the homogeneity of solidified soil in practical engineering applications.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.51578147)Fundamental Research Funds for the Central Universities(Grant No.2242020R20025)Ningxia Science and Technology Department(Grant No.2020BFG02014).
文摘In most coastal and estuarine areas,tides easily cause surface erosion and even slope failure,resulting in severe land losses,deterioration of coastal infrastructure,and increased floods.The bio-cementation technique has been previously demonstrated to effectively improve the erosion resistance of slopes.Seawater contains magnesium ions(Mg^(2+))with a higher concentration than calcium ions(Ca^(2+));therefore,Mg^(2+)and Ca^(2+)were used together for bio-cementation in this study at various Mg^(2+)/Ca^(2+)ratios as the microbially induced magnesium and calcium precipitation(MIMCP)treatment.Slope angles,surface strengths,precipitation contents,major phases,and microscopic characteristics of precipitation were used to evaluate the treatment effects.Results showed that the MIMCP treatment markedly enhanced the erosion resistance of slopes.Decreased Mg^(2+)/Ca^(2+)ratios resulted in a smaller change in angles and fewer soil losses,especially the Mg^(2+)concentration below 0.2 M.The decreased Mg^(2+)/Ca^(2+)ratio achieved increased precipitation contents,which contributed to better erosion resistance and higher surface strengths.Additionally,the production of aragonite would benefit from elevated Mg^(2+)concentrations and a higher Ca^(2+)concentration led to more nesquehonite in magnesium precipitation crystals.The slopes with an initial angle of 53°had worse erosion resistance than the slopes with an initial angle of 35°,but the Mg^(2+)/Ca^(2+)ratios of 0.2:0.8,0.1:0.9,and 0:1.0 were effective for both slope stabilization and erosion mitigation to a great extent.The results are of great significance for the application of MIMCP to improve erosion resistance of foreshore slopes and the MIMCP technique has promising application potential in marine engineering.
基金funded by the National Natural Science Foundation of China(Grant No.51578147)the Science and Technology Department of Ningxia(Grant No.2020BFG02014)the Trans-portation Department of Ningxia(Grant No.202000173).
文摘Enzyme-induced carbonate precipitation (EICP) is an emerging technique to improve the soil and most studies are carried out at room temperature. However, considering some foundations are in high-temperature environments (>40 ℃), the higher urease activity at high temperature results in the solidification inhomogeneity, limiting the application of EICP. The higher urease activity at high temperature hampers the application of EICP because of solidification inhomogeneity. The garlic extract has been used as a type of urease inhibitor in medical science and food engineering. Here, we propose to use it to control urease activity for sand solidification at high temperature. The effects of garlic extract addition on urease activity and precipitation rates for calcium carbonate (CaCO_(3)) were studied. Extra tests were conducted to study the effect of garlic extract addition on the solidification homogeneity. The results showed that the garlic extract addition significantly decreased urease activity. To reduce the rate of CaCO3 precipitation at different temperatures, a suitable concentration of garlic extract was necessary to obtain a suitable urease activity. In the sand solidification test, garlic extract addition resulted in a smaller difference in sonic time values or CaCO_(3) contents at different parts of samples. The improved solidification homogeneity can achieve higher strength. The correlation between sonic time values and CaCO_(3) content was higher than that between CaCO3 content and strength. Appropriate concentrations of garlic extract were obtained at 35 ℃, 40℃, 45 ℃, 50 ℃, and 55 ℃. The proposed garlic extract addition method was significant to improve the homogeneity of solidified soil in practical engineering applications.
