Strength and cracking behavior of weak expansive soil improved by basalt fiber

The engineering geological problems caused by expansive soil have become a key factor restricting urban geological safety. Objective and MethodsIn order to study the effect and mechanism of basalt fiber in improving expansive soil, weak expansive soil from Three Gorges Airport, Yichang, Hubei, was taken as the research object. By adding 0.2%, 0.4%, and 0.6% basalt fiber to the soil, triaxial compression test and dry-wet cycle test were conducted, combined with digital image processing technology, to investigate the strength of the improved soil and the variation of surface cracks under the dry-wet cycle with fiber content. ResultsThe results showed that the content of basalt fiber had a significant effect on the cohesion of the improved soil but had no significant effect on the internal friction angle. When the content of basalt fiber was 0.4%, the cohesion of the improved soil increased by 57.1%. The improvement coefficient for different basalt fiber contents was greater than 1.0, with the best improvement effect occurring at 0.4%. After the first dry-wet cycle, no cracks were observed in either the improved soil or the untreated expansive soil. The crack area ratio and fractal dimension of the basalt fiber-improved soil in subsequent cycles were smaller than those of the original soil. The maximum difference in the crack area ratio increased from 2.41% to 4.54%, and the maximum difference in the fractal dimension decreased from 0.058 to 0.037. When the content was 0.4%, the fiber had the best effect in inhibiting the cracking of the soil. The fiber embedded in the soil reduced the stress concentration at the crack tip, which limited the development of the crack. ConclusionThe research results can provide valuable references for the engineering application of basalt fiber-improved weak expansive soil at the regional scale.