Effect of Straw Characterization on the Mechanical Behavior of Compacted Straw-Reinforced Soils

Straw reinforcement improves the mechanical properties of soil matrices by uniformly incorporating dispersed straw materials, demonstrating advantages in strength enhancement, toughness improvement, and deformation control. This study aims to compare the reinforcement effects of different types of straw on soil and clarify the optimal method for straw-based soil stabilization. For wheat straw-reinforced soil using different processing methods (straw segment, straw powder, and straw ash) and mass contents, the basic geotechnical properties of each mixture were first determined. Triaxial tests were then performed under varying confining pressures and compaction conditions to assess the strength and modulus characteristics of the different reinforced soil specimens, and the microstructural characteristics of fiber-reinforced soil were investigated using scanning electron microscopy (SEM) analysis. The experimental results indicated that the strength and ductility of soils increased significantly with the addition of straw. The optimal performance of straw-reinforced soils occurred at 0.3% content. The elastic modulus increased by 85%, 64%, and 57% under confining pressures of 50 kPa, 100 kPa, and 200 kPa, respectively. At 200 kPa, straw segments provided the highest modulus increase of 57%, while straw ash achieved the greatest strength improvement of 97%. Furthermore, considering both compaction effects and cost efficiency, a compaction degree of 95% is recommended for straw-reinforced soil in engineering applications. Based on scanning electron microscopy, it was observed that the distribution characteristics of different straw types within the soil exhibit distinct patterns. This study aims to provide data to support the efficient utilization of straw materials in engineering applications.