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Aeolian sand is mainly distributed in arid and rainless desert areas. It is a special soil with loose structure, fine and uniform particles, poor self-stability and not easy to compact. For discussion The law of microbial solidification of large-volume aeolian sand, the use of microbial induced calcium carbonate precipitation technology, the use of Bacillus pasteurianus, the microbial addition to the aeolian sand column in a saturated state In the solid test, the bacterial concentration at different depths in the sand column as well as the bacterial adsorption capacity, enzyme activity, urea concentration and other indicators were determined. At the same time, the dryness of the cured samples at different depths was analyzed. The changing law of density, unconfined compressive strength and calcium carbonate content. The test results show that the best standing time of the bacteria in the sand column is 4 hours, and the best standing time of the cementing liquid in the sand column is 4 hours. Set the time to 24h. By pouring the aeolian sand with Bacillus pasteurianus and cementitious liquid, calcium carbonate crystals can be formed between the aeolian sand particles, thereby bonding the sand particles together. To form a whole with a certain strength. The unconfined compressive strength of solidified aeolian sand is between 0.43 and 7.13 MPa. Microbial-induced calcium carbonate precipitation technology to solidify aeolian sand The effective depth is 0.2 to 0.7 m. The dry density, unconfined compressive strength and calcium carbonate content at different positions of the solidified sand column have similar changes with depth, and they all increase first and then decrease. The peak is reached at about 0.4 m. Therefore, the use of microbial induced calcium carbonate precipitation technology can effectively reinforce aeolian sand in deserts, and can significantly improve the engineering properties of aeolian sand. [ABSTRACT FROM AUTHOR]

The coefficient of safety is an important index for the evaluation of slope stability. The safety coefficients calculated based on different instability criteria are significantly different, and the variability of the results will directly affect the evaluation of the stability state of slopes. In this paper, taking the step-type excavated slope of the Wanhuashan Trench Construction Project as the object, FLAC3D finite difference software was used to calculate the safety coefficient of loess slopes based on three different types of instability criteria, namely the calculation non-convergence criterion, the plastic penetration criterion and the displacement abruptness criterion, and to compare and analyze the differences, advantages and disadvantages of the evaluation results of the three criteria. The results of the study shows that there is a certain difference in the magnitude of safety coefficients obtained by using different instability criteria, with the order of magnitude being displacement abrupt change criterion > computational non-convergence criterion > plastic penetration criterion. The computational non-convergence criterion is easy to use and fast to solve, but does not show the change in the plastic zone of the slope during the discounting process. The plastic penetration criterion is not suitable as a criterion for slope instability on its own, but needs to be combined with the unbalanced force rate to be assessed, but it can show the area of shear damage and stretching of the slope. The sudden change of displacement criterion is tedious to solve, but the solution process truly reflects the critical damage state due to the change of slope displacement. For practical conditions such as loess slopes, it is recommended to use the fast computational non-convergence criterion to evaluate the slope stability in combination with the plastic zone penetration and the slope displacement change. [ABSTRACT FROM AUTHOR]