In this study, the potential application of slag-fly ash-based geopolymers as stabilizers for soft soil in sulfate erosion areas was investigated to promote environmental protection and waste residue recycling. The changes in the physical and mechanical properties and microstructure characteristics of cement-stabilized soil/geopolymer-stabilized soil under sulfate erosion were comparatively studied through tests such as appearance change, mass change, strength development, and microscopic examination. The results show that the sulfate resistance of stabilized soil is significantly affected by the stabilizer type. In the sulfate environment, the cement-stabilized soil significantly deteriorates with erosion age due to the expansion stress induced by AFt, while the geopolymer-stabilized soil exhibits excellent sulfate resistance. The slag-fly ash ratio (10:0, 9:1, 8:2 and 7:3) is an important factor affecting the sulfate resistance of geopolymer-stabilized soils, and the preferred value occurs at 9:1 (G-2). When immersed for 90 d, the unconfined compressive strength value of G-2 is 7.13 MPa, and its strength retention coefficient is 86.6%. The N-A-S-H gel formed by the polymerization in the geopolymer contributes to hindering the intrusion of sulfate ions, thereby improving the sulfate resistance of stabilized soil. The research results can provide a reference for technology that stabilizes soil with industrial waste in sulfate erosion areas.

To promote the application of the bamboo grid in the soil–rock mixture subgrade in mountain areas, the mechanical properties of bamboo reinforcement were investigated in this study, and the reinforcement effect and interface characteristics of uniaxial/biaxial bamboo grid on the soil–rock mixture under different vertical loads was comparatively analyzed. The results show that the tensile force (2% elongation) of the bamboo reinforcement is 50.21 kN/m, and its average tensile strength is 236.01 MPa. Moreover, bamboo reinforcement has excellent shear and flexural properties. In general, the reinforcement effect of the biaxial bamboo grid on the soil–rock mixed subgrade is better than that of the uniaxial bamboo grid. In the case of using a uniaxial bamboo grid, its pull-out curve is generally a strain-softening type. As for the biaxial bamboo grid, due to the existence of bite force, its pull-out curve usually presents a strain-hardening type. Compared with the uniaxial bamboo grid, the friction coefficient of the reinforcement–soil interface using the biaxial bamboo grid is higher, and the interfacial shear stress is increased by 72.2–91.2%.