Study on the compressive performance and numerical simulation of fiber-reinforced geopolymer stabilized aeolian sand subgrade materials

To enhance the compressive strength and toughness of geopolymer-stabilized aeolian sand subgrade materials, and to promote the utilization of aeolian sand resources, polypropylene fibers are incorporated into geopolymer solidified aeolian sand materials. Unconfined compressive strength tests are conducted on specimens prepared under different mixing schemes. The strength formation mechanism and fiber toughening crack resistance mechanism are revealed at the microscopic level using SEM (Scanning Electron Microscopy) technology. The finite element numerical simulation software FLAC3D 6.0 is used to establish a numerical model of the highway, analyzing the subgrade dynamic response and maximum displacement of geopolymer-stabilized aeolian sand subgrade materials under various vehicle speeds in the conditions of optimal fiber length and the optimal amount of fiber. Research results show that when the NaOH content is 1.5%, the fiber content is 0.5%, and the fiber length is 12 mm, it constitutes the optimal mix ratio for the specimen, with the peak UCS (Unconfined Compressive Strength) and residual UCS reaching their optimal values. Slag and fly ash form a three-dimensional topological network structure under the action of the alkaline solution, which promotes the bonding between the aeolian sand particles and between the fibers and the matrix. The three-dimensional network structure of fibers within the matrix effectively inhibits the dislocation of aeolian sand particles and suppresses the development and expansion of cracks, playing a key role in enhancing the residual UCS of the specimen. Using the finite element FLAC3D 6.0 numerical simulation software, it was found that when the road subbase material is fiber-reinforced geopolymer stabilized aeolian sand material, the dynamic response impact area of the subbase is significantly smaller than that of the geopolymer stabilized aeolian sand. The research results provide a reference for the practical application of fiber-reinforced geopolymer stabilized aeolian sand materials in road subbase engineering.