| Summary: | 碩士 === 國立中興大學 === 土木工程學系所 === 106 === Ground improvement method is often carried out by the dynamic compaction method or cement-based material grout method. But these methods can’t meet the requirements of energy saving and environmental protection, which is more and more important for the engineering. The purpose of this study is to investigate the feasibility of the soil bearing strengthening capacity through microbe-induced calcium carbonate precipitation (MICP). It’s a new ecological method that is friendly to the environment. The bacterial culture process and the basic properties of the bacteria were discussed firstly, and the cementation test of different soil remolded specimens was carried out to explore the effects and possible limitations of the MICP method. Finally, a small-scale field stratum strength improvement by MICP method was tested. The result of the stratum strength improvement test was examined by both standard penetration test and spectral analysis of surface wave method.
The test results showed that the shear wave velocity of standard sand remolded specimens, which were cemented by the MICP method, increased with the curing time. The compressive strength of the remolded specimens can raise up to 3 ~ 12 kPa. The test results also showed that the compressive strength of silty sand remolded specimen increased from 353kpa to 2802kpa. The above test proves the efficacy of the MICP method can strengthen the soil bearing capacity.
In the field test of the MICP method, the standard penetration test results showed that the MICP method has a significant improvement effect in the silty fine sand layer at a depth of 1.05 m to 1.5 m, and obvious improvement in the high-density grouting area at a depth of 2.55 to 3 meters. But there is no apparent improvement below 4.8 m depth. According to the results of the spectral analysis of surface wave method, the shear velocity in the deep stratum increases. The study considers that the bacteria grow and keep cementing soil particles lead to such a result. According to the above test results, it is indeed feasible to apply the MICP technology to strengthen the soil bearing capacity.
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