Minimum dataset.

Granite residual soil exhibits inferior mechanical properties, which may lead to slope instability and embankment settlement. Microbial solidification technology offers an environmentally sustainable and highly effective approach for the improvement of such soils. To enhance the strength properties of granite residual soil in the Hanzhong region, three urease-producing Bacillus species, including Bacillus velezensis, Bacillus subtilis, and Bacillus tequilensis, are extracted from the soil in the same area, and solidification improvement experiments are conducted by changing the concentration of the cementing solution. The experimental results indicate that all three bacterial strains can substantially enhance the shear strength of soil. The optimal improvement effect for each strain is observed when the cementing solution concentration reaches 2 mol/L. Notably, Bacillus subtilis exhibits the greatest increase in internal friction angle, rising by 145.32% compared to the unimproved. In contrast, Bacillus tequilensis shows the highest improvement in cohesion, with a maximum increase of 316.19%. The solidification effect differed among different bacterial strains, with B. tequilensis and B. velezensis exhibiting better performance in high-concentration cementing solutions. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis reveal that the calcium carbonate precipitates in the soil solidified by these three types of bacteria can strongly bind to the soil particles, confirming the improvement effect at the microscopic level. This study provides an eco-friendly and cost-effective improvement method for the engineering application of granite residual soil, which plays an important role in improving the quality and decreasing the cost of artificial slope filling, roadbed filling, and foundation pit backfilling in areas with granite residual soil.花岗岩残积土力学性能欠佳，易引发边坡失稳与路堤沉降问题。微生物固化技术为这类土的改良提供了一种环境友好且高效的技术路径。为提升汉中地区花岗岩残积土的强度性能，研究人员从该区域土壤中分离得到3株产脲酶芽孢杆菌，分别为贝莱斯芽孢杆菌（Bacillus velezensis）、枯草芽孢杆菌（Bacillus subtilis）及特基拉芽孢杆菌（Bacillus tequilensis），并通过改变胶结液浓度开展固化改良试验。试验结果表明，3株菌株均可显著提升土壤的抗剪强度。当胶结液浓度达到2mol/L时，各菌株均能实现最优改良效果。值得注意的是，枯草芽孢杆菌对内摩擦角的提升幅度最大，较未改良组提升了145.32%；相较而言，特基拉芽孢杆菌对黏聚力的改良效果最优，最大提升幅度达316.19%。不同菌株的固化效果存在差异：特基拉芽孢杆菌与贝莱斯芽孢杆菌在高浓度胶结液条件下表现更优。扫描电子显微镜（SEM）与X射线衍射（XRD）分析结果显示，经3株细菌固化的土壤中生成的碳酸钙沉淀物可与土壤颗粒紧密结合，从微观层面验证了改良效果。本研究为花岗岩残积土的工程应用提供了一种环境友好且经济高效的改良方法，对提升花岗岩残积土分布区域人工边坡填筑、路基填筑及基坑回填的施工质量、降低工程成本具有重要意义。