Influence of Compaction and Water Content on the Shear Performance of Gobi Soil as a Sustainable Construction Material

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.