Laboratory triaxial compression tests were conducted to investigate the stress-strain-volumetric responses of geotextile-reinforced sand and the mobilization and distribution of reinforcement strain/loads and soil-geotextile interface shear stress within reinforced soil. Geotextile-reinforced sand specimens were tested while varying the confining pressures and number of geotextile reinforcement layers. A digital image-processing technique was applied to determine residual tensile strain of the reinforcements after tests and to estimate reinforcement tensile loads. Experimental results indicate that the geotextile reinforcement enhanced peak shear strength and axial strain at failure, and reduced loss of post-peak shear strength. The reinforced specimen had higher shear strength when compared with that of unreinforced soil after deforming by 1-3% of axial strain, which indicates that the geotextile requires a sufficient deformation to mobilize its tensile force to improve the shear strength of reinforced soil. For each reinforcement layer, mobilized tensile strain peaked at the center of the reinforcement and decreased along the radial direction, while the interface shear stress was zero at the center and peaked at a distance of 0.5-07 reinforcement radius from the center. The mobilized tensile strain of reinforcement increases as confining pressure and number of reinforcement layers increase. This work also demonstrates that the strength difference between reinforced and unreinforced soil was strongly correlated with the sum of maximum mobilized tensile forces of all reinforcement layers, indicating that mobilized tensile force of reinforcements directly improved the shear strength of reinforced soil. Last, a number of analytical models to predict peak shear strength of reinforced soil are verified experimentally. This verification demonstrates that mobilized tensile force rather than ultimate tensile strength can be used in analytical models.