电渗生物法灌浆改善粉土中碳酸盐沉积分布的试验研究

EXPERIMENTAL STUDY OF IMPROVING CARBONATE DEPOSITION DISTRIBUTION IN SILT BY EBM GROUTING

为改善生物灌浆诱导碳酸盐在粉土中沉积扩散范围不足和沉积的不均匀性,采用电渗生物灌浆方法(EBM)在粉土中进行灌浆试验。首先研究了不同电压梯度下,脲酶活性的变化规律,在此基础上研究电场下微生物诱导碳酸钙在土中的沉积规律,并与重力灌浆和0.3 MPa低压灌浆方式的沉积效果进行比较。试验结果表明:脲酶活性随电压梯度的增大而降低;电压梯度影响碳酸盐的沉积和分布,当电压梯度在1.0 V/cm附近时,测得的碳酸钙含量沿场强方向变化范围为5.8%~9.6%,碳酸钙的沉积量较多,分布较均匀,而电压梯度为0.5,1.5 V/cm时碳酸钙沉积相对减少,故EBM灌浆的电压梯度宜取1.0 V/cm左右,过低,电渗驱动作用不明显,超过1.5 V/cm,生物活性受到抑制,碳酸钙沉积量反而降低;同土质条件下,重力灌浆的碳酸钙分布范围为0.8%~10.6%,0.3 MPa低压注浆为3.9%~10.2%,故电渗条件有利于生物质在土体孔隙中扩散,使碳酸钙分布更均匀,是一种值得关注的生物灌浆方法。

In order to improve sediment heterogeneity and deposition of carbonate in silt induced by bio-grouting,an experimental study of EBM（Electro-Bio-Grouting Method） was performed in silt.The changes of urease activity were studied under different voltage gradients.Then,the EBM tests were conducted to study the sediment law of calcium carbonate in silt induced by microbial in the electric field.Finally,EBM model tests results were compared with that of gravity grouting and 0.3 MPa low pressure grouting.The results showed that urease activity decreased with the increase of voltage gradient,and voltage gradient influenced the deposition of carbonate.When the voltage gradient was near 1.0 V/cm,the variation range of the measured Ca CO3 content was from 5.8% to 9.6% along the electric field intensity,there were more sediments and the deposition was relatively uniform.However,when the voltage gradient was 0.5 V/cm and 1.5 V/cm,the sediment of calcium carbonate was relatively reduced.So the appropriate voltage gradient of EBM grouting should be about 1.0 V/cm.When the voltage gradient was too low,electroosmotic effect was not obvious.When the voltage gradient exceeded 1.5 V/cm,the biological activity was inhibited and the calcium carbonate sediment decreased.The calcium carbonate deposition of gravity grouting was 0.8% to 10.6%,while that of 0.3 MPa low pressure grouting was 3.9% to 10.2%.Therefore,electroosmotic conditions could promote the diffusion of biomass in soil pore.The calcium carbonate desposition induced by EBM was more uniform,which was worthy of more attention.