微生物固化纤维加筋砂质黏性紫色土试验研究

Experimental Study on Bio-cemented Solidification Fiber-reinforced Sandy Clayey Purple Soil

微生物诱导方解石沉积(MICP)技术是一种新型土体加固措施,大量的研究表明,土体加固强化的同时也使得土体破坏呈现明显脆性。为了改善微生物固化紫色土的脆性破坏模式,采用纤维加筋与微生物固化相结合的加固方法,将质量分数为0.4%、0.6%、0.8%的纤维与紫色土混合,然后采用巨大芽孢杆菌和钙盐溶液对土样进行不同灌浆次数的固化试验(3次、5次、7次、9次)。通过无侧限压缩试验测定试样抗压强度,洗酸法试验测定试样碳酸钙含量,烘干法测定试样干密度,结果表明:(1)在微生物固化紫色土中掺入纤维,能显著提高试样固化后的无侧限抗压强度和峰值强度对应的轴向应变,改善了土体破坏时的韧性;(2)纤维掺量影响微生物固化紫色土的力学性质,其强度随纤维掺量总体上呈先增大后减小的趋势,最优纤维掺量为0.6%;(3)随着固化时间增加,试样的碳酸钙生成量和干密度逐级增加,强度与碳酸钙生成量呈正相关且有效碳酸钙沉积越来越少,强度趋于稳定;(4)纤维加筋可以提高碳酸钙沉积的效率和产量,土样内生成的碳酸钙对纤维加筋效果具有强化作用。研究成果可以为纤维加筋与MICP固化相结合的土体加固技术应用提供指导和参考。

The microbial-induced calcite precipitation(MICP)technology is a new measure,but a large number of studies have shown that soil reinforcement is also accompanied by obvious brittle failure.In order to improve the brittle failure mode of bio-cemented purple soil,a combination of fiber reinforcement and microbial cementation was adopted.Glass fiber with a mass fraction of 0.4%,0.6%,and 0.8%was mixed with purple soil,the bacillus megaterium and the calcium salt solution were used to conduct soil cemented tests with different grouting times(3 times,5 times,7 times,9 times).The compressive strength of the sample was determined by an unconfined compression test.The calcium carbonate content of the sample was measured by the acid washing test.The dry density of the specimen coas tested with the oven drying method.The results show that:(1)The incorporation of fibers into the bio-cemented purple soil can significantly increase the axial strain corresponding to the unconfined compressive strength and peak strength of the sample after curing,and improve the tenacity when the soil is damaged.(2)Fiber content affects the mechanical properties of microbial solidified purple soil.Its strength generally increases first and then decreases with fiber content and the optimal fiber content is 0.6%.(3)As the reinforce time increased,the amount of calcium carbonate produced and the dry density increase constantly,the strength is positively correlated with the amount of calcium carbonate produced,the effective calcium carbonate deposits are becoming less,and the strength tends to be stable.(4)Fiber reinforcement can increase the efficiency and the productivity of calcium carbonate,the calcium carbonate generated in the soil sample has a reinforcing effect on the fiber reinforcement.The research results can provide guidance and reference for the application of soil reinforcement technology combined with fiber reinforcement and MICP cementation.