Two alternative techniques, the lime stabilization technique (LST) and the geogrid reinforcement technique (GRT), are both useful to stabilize expansive soil slopes, but their impacts on the environment need be further evaluated. Based on a case study, two techniques as well as their construction processes were introduced. The energy consumption and carbon dioxide (CO₂) emissions were investigated by the life cycle assessment (LCA). The sensitivity analyses were carried out, including the lime content for LST, the reinforcement spacing for GRT, the embankment height, delivery distance, and treatment width for both techniques. From the LCA results, with the GRT, the energy consumption and CO₂ emissions can be reduced by 7.52% and 57.09%, respectively. The main sources of two techniques are raw material production, soil transportation, and paving stage while the CO₂ emissions of lime production are about 11.68 times of those of geogrid production. From the sensitivity analysis results, as the lime content of LST increases by 1%, the total energy consumption and CO₂ emissions increase by 8.27% and 13.16%, respectively; as the reinforcement spacing of GRT increases by 0.05 m, the total energy consumption and CO₂ emissions increase by 1.63% and 0.69%, respectively; as the embankment height increases by 1 m, the increase rates of energy consumption and CO₂ emissions of LST are 1.68 and 1.61 times of those of GRT, respectively. In this project, when the embankment height is less than 10 m, the geogrid technique has the advantages of energy‐saving and emission‐reduction. It was found that the GRT is not sensitive to the change of delivery distance and treatment width and significantly reduces the environmental impacts, especially in reducing the impact of global warming.

Rainfall is the main factor leading to the landslide of expansive soil slope. To deeply understand the instability mechanism of expansive soil slope under rainfall conditions, it is necessary to clarify the strength attenuation mechanism of expansive soil caused by water absorption and swelling. Therefore, the improved constant volume direct shear test was used in this study to compare with the conventional test, focusing on the variation of effective shear strength parameters with dry density (volume). The micromechanism of expansive soil strength attenuation is further studied, and the influence of expansive soil on slope stability is analyzed by numerical calculation. The results show that the improved direct shear apparatus and method can keep the volume of expansive soil specimens unchanged before and after shear and obtain the real effective shear strength parameter of soil. Under the same conditions, the shear strength parameter of the improved direct shear test is lower than that of the conventional direct shear test. The rapid thickening of the lamellar structure of montmorillonite in expansive soil will lead to the fragmentation and dispersion of clay particles, which is one of the fundamental reasons for the strength difference between expansive soil and ordinary clay. In slope stability analysis, the effect of swelling on the shear strength of slope cannot be ignored and should be considered in engineering design.

In order to improve the ability of the flexible support structure to resist, recover and adapt to the failure of expansive soil slope, it is necessary to analyze and study its structural resilience systematically. Based on the long-term field monitoring test of expansive soil slope with flexible support along the south line of the Guinan key project, combined with the whole life cycle assessment (LCA), this paper discusses the theory and method of resilient design of expansive soil slope with a flexible support structure. The results show that the variation trend of geogrid strain is basically consistent with that of soil pressure at the side of the slope. It increases gradually with the increase in rainfall in the rainy season. When the rainfall decreases significantly in the dry season, the geogrid will shrink accordingly to realize the periodic regulation of lateral deformation of expansive soil. The life cycle assessment analysis shows that the carbon emission of the flexible support structure is 10% of that of the rigid support structure, and the resource and energy consumption of the flexible support structure is about 50% lower than that of the rigid support structure.