Wind and solar power generation, a clean and renewable energy source, relies on stable foundations in Gobi soil regions, where the mechanical properties of the local soil are critical. This study investigated the shear behavior of Gobi soil from Dabancheng District, Urumqi, China, through 60 direct shear tests, analyzing the effects of water content (4%, 6%, 8%, 10.5%, 12.5%) and compaction degree (87%, 90%, 95%). Results indicate that water content governs the strain response: low moisture leads to strain-softening, while optimum or higher moisture causes strain-hardening. The relative softening coefficient decreases with rising water content and vertical stress but increases with compaction. Peak shear strength grows with vertical stress and compaction, yet peaks and then declines as water content increases. Shear modulus improves significantly under low water content and high compaction. Cohesion initially rises and then falls with increasing water content, while the internal friction angle decreases continuously. Both generally increase with compaction, though cohesion gains diminish at high moisture levels. Binary quadratic equations were established to relate mechanical parameters to compaction and water content. The findings provide a reference for selecting shallow foundation design parameters for wind and solar installations in Gobi regions.

The poor engineering properties of Gobi soil, such as low strength and poor water stability, pose challenges for foundations in arid regions, especially large photovoltaic plants. This study examines the effect of polypropylene (PP) fiber reinforcement on Gobi soil from Dabancheng, Xinjiang. Laboratory tests including unconfined compressive strength, direct shear (orthogonal experimental design), slake durability, and scanning electron microscopy were performed to investigate the influences of fiber length (6, 9, 12 mm), fiber content (0.3–1.1% by dry soil mass), and water content (4–12.5%). Results indicate that PP fibers change the failure mode from brittle to ductile. The optimal combination (9 mm fiber length, 0.7% content, and Proctor optimum water content of 10.5% corresponding to maximum dry density) improves cohesion by 122% (reinforcement coefficient K = 2.22). Moreover, fibers alter the disintegration behavior from complete to stable partial disintegration; the 12 h disintegration ratio decreases from 100% to 13% under optimal conditions. Microstructural analysis shows that an appropriate fiber content creates a uniform three-dimensional reinforcing network, enhancing mechanical interlocking and fiber bridging, whereas excessive fiber leads to agglomeration and increased pore connectivity, degrading overall performance. This study provides a low-carbon, sustainable soil stabilization method and practical design parameters for Gobi desert infrastructure.