膨润土辅助微生物固化砂土的试验研究

Experimental Study on Bentonite-assisted Microbial Solidification of Sandy Soil

为研究膨润土种类对MICP效果的影响,分别选用钙基和钠基膨润土,在胶结液为1mol/L的条件下添加不同质量分数(1%、2%、3%、4%)的膨润土与砂土混合,采用拌合法进行固化试验,结果认为:相较于钠基膨润土,添加了钙基膨润土的菌液初始pH值更低,脲酶活性更高;钙基膨润土固化后试样的无侧限抗压强度均高于钠基膨润土试样,故MICP固化过程中的钙基膨润土更有优势。为了研究钙基膨润土辅助微生物固化砂土的最佳条件,同时改变钙基膨润土掺量和胶结液浓度进行制样并开展固化后的强度测试,结果认为:钙基膨润土掺量对试样强度的影响与胶结液浓度密切相关,胶结液浓度较低时,试样的强度随着钙基膨润土掺量的增加而增强;胶结液浓度较高时,试样的强度随着钙基膨润土掺量的增加先增强后减弱;研究范围内钙基膨润土辅助微生物固化砂土的最优条件为2 mol/L的胶结液浓度和2%的膨润土掺量。

In order to study the effect of bentonite types on MICP,calcium-based and sodium-based bentonites were selected,and different mass ratios(1%,2%,3%,4%)of bentonite were added and mixed with sandy soil under the condition of 1mol/L of the cementation solution,and the curing tests were conducted by mixing method.The results show that the initial pH value of the bacterial solution with the addition of calcium-based bentonite was lower and the urease activity was higher compared with that of sodium-based bentonite,and the unconfined compressive strength of the cured specimens of calcium-based bentonite was all higher than those of the sodium-based bentonite specimens.Therefore,calcium-based bentonite in the MICP curing process is more advantageous.In order to study the optimal conditions for calcium-based bentonite-assisted microbial curing of sandy soil,specimens’preparation and strength test were carried out by changing the calcium bentonite content and the concentration of the cementation solution.The results show that the influence of calcium-based bentonite content on specimens’strength is closely related to the concentration of the cementation solution.When the concentration of the cementation solution is low,the strength of the specimens increases with the increase of calcium-based bentonite content.When the concentration of the cementation solution is high,the strength of the specimens increases first and then decrease with the increase of the content of calcium-based bentonite.The optimal conditions for calcium-based bentonite assisted microbial solidification of sandy soil within the research range are 2mol/L cementation solution concentration and 2%bentonite content.