Microbial solidified sand effectively enhances the strength of the soil, but it will cause brittle failure. In order to reduce the impact of microbial solidification sand brittleness, an improved method for adding carbon fiber to microbial solidified sand is proposed. The qualitative analysis was based on unconfined compressive strength test, calcium carbonate content determination, and penetration test. The results show that the addition of fiber in the microbial solidified sand can significantly increase the unconfined compressive strength of the sample. The unconfined compressive strength of the sample increases first and then decreases with the increase of fiber addition. The addition of fibers during the soil process enhances the toughness of the specimen and causes plastic damage during the failure of the specimen. Based on the analysis of the microstructure of the sample, the effect of fiber bundles on the strength characteristics of the sample is discussed when the fiber content is higher than the optimal fiber content. The addition of carbon fiber to microbial solidified sand can greatly improve the strength of the sample and increase the toughness, which plays a positive role in improving the safety and stability of the project.
Based on the shield tunnel engineering in weathered granite stratum in Xiamen, Stochastic calculations, by combining the random field theory and the finite difference analysis together with Monte Carlo simulation, are used to carry out the change law of the characteristics of surface deformation curve and surface deformation model. Results show that with the increase of the vertical scales of fluctuation, the decrease of the transverse scales of fluctuation or the increase of the coefficient of variation, the low peak distribution characteristics of the location of the maximum surface settlement induced by shield tunneling become more obvious, and the randomness and chaos of the shape of surface deformation curve gradually increase. The diversity of surface deformation model is affected by parameter correlation and randomness. Under the condition of small transverse scales of fluctuation and large vertical scales of fluctuation, the sensitivity of coefficient of variation to surface deformation mode is limited.
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