The factors influencing geogrid–soil interface characteristics are critical design parameters in some geotechnical designs. This study describes pull-out tests performed on gravelly soils commonly encountered in the Xinjiang region and reinforced with two types of geogrids. The factors affecting the geogrid–gravelly soil interface properties are investigated with different experimental loading methods (pull-out velocity, normal stress), geogrid types, and soil particle size distributions and water contents. The ultimate pull-out force increases with the normal stress and pull-out velocity. Furthermore, with increasing coarse particle content and water content, the ultimate pull-out force increases and then decreases sharply. Based on these research results, this paper provides reasonable parameters and recommendations for the design and pull-out testing of reinforced soil in engineering structures. In reinforced soil structure design, the grid depth should be increased appropriately, and the coarse particle content of the overlying soil should be between 30 and 40%. During construction, the gravelly soil should be compacted to the maximum compaction at the optimal water content, and the structure should have a reasonable waterproofing system. According to the calculation results of the interface strength parameters, the uniaxial geogrid–gravelly soil interface has a high cohesive force c_sg, which should not be ignored in reinforced soil structure design.

To enhance the mechanical and durability properties of cement-fly ash stabilized aeolian sand and crushed stones, the synergistic optimization effects of basalt fibers and polycarboxylate superplasticizer were investigated. First, two full factorial experiments were conducted to evaluate the individual and combined effects of basalt fiber volume content and polycarboxylate superplasticizer mass content. Then, four mix proportions were selected to verify the durability optimization. Finally, SEM, EDS, and XRD were used to elucidate the underlying micro-mechanisms. The results indicate that the optimal combination was 0.1% volume content of 12-mm-long basalt fibers and 1.0% mass content of polycarboxylate superplasticizer, which yielded a compressive strength of 13.3 MPa and a splitting tensile strength of 1.14 MPa at 28 days. Compared to the control group and individual addition of basalt fibers or polycarboxylate superplasticizer, the group with both basalt fibers and polycarboxylate superplasticizer had 33.00%, 16.67%, and 14.66% higher compressive strength and 52.00%, 31.03%, and 28.09% higher splitting tensile strength, respectively. Furthermore, the combined optimization improved the durability, decreased the thermal shrinkage by 49.85%, 32.35%, and 28.84%, and decreased the drying shrinkage by 68.95%, 33.15%, and 47.58%. The micro-experiments demonstrate that the bridging effect of basalt fibers during micro-crack formation and the synergistic action of polycarboxylate superplasticizer enhanced the uniformity and density of the mixture and that they are the primary factors that contribute to the strength development. Therefore, cement-fly ash stabilized aeolian sand and crushed stones can be optimized by using basalt fibers and polycarboxylate superplasticizer.

The durability of cement–fly ash stabilized aeolian sand gravel base (CFSAGB) materials was enhanced using basalt fiber (B) and polycarboxylate superplasticizer (P). Four BP-CFSAGB mixtures with varying B–P dosages were prepared. Mechanical properties were evaluated after freeze–thaw cycling in multiple salt environments. Strength was significantly improved. The optimal mix showed 32.2% higher compressive strength and 42.9% higher tensile strength than the control after 10 freeze–thaw cycles in a 0.5% NaCl–5% Na₂SO₄ solution. Deterioration was found to be a physicochemical process dominated by physical damage. Basalt fibers alleviated internal stresses through crack bridging. The superplasticizer improved particle dispersion and stabilized hydration products. Although acting independently, their effects proved complementary. Microstructural analysis via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) confirmed the formation of denser matrices and more stable hydration phases in the modified mixtures. These findings demonstrate that the combined use of B and P can significantly improve the freeze–thaw resistance of cement-stabilized granular base layers. The results provide mechanistic insight and technical support for the design of durable pavement base courses in salt-affected regions.