Abstract: Under the increasingly complex and harsh geological environment of engineering, the quality requirements for grouting reinforcement are becoming more stringent.Establishing a scientific and reasonable grouting effect prediction and evaluation method has important theoretical significances and research values.By applying fractal theory to describe the intricate spatial structure and variation characteristics of sandy soil, tortuosity was defined as the square of the ratio of the actual flow length (Le) to the theoretical flow length (L), by which the relationship between the surface porosity and bulk porosity of sandy soil's porous media was induced.Subsequently, using surface porosity and bulk porosity as variables, a theoretical prediction method for calculating the strength and stiffness of grouting-reinforced masses was established based on fractal theory and the Mori-Tanaka method.This method was then applied to an actual engineering project for validation.The results demonstrate that the strength of the grouting-reinforced mass is governed by the minimum strength under both tensile and shear failure modes, while stiffness depends on factors such as the matrix's elastic constant, the proportion of inclusions, and the Eshelby tensor.The errors between on-site measured values and the predicted values were only 18.6% (strength) and 16.6% (stiffness), respectively.This confirms that the proposed model accurately analyzes the mechanical response of tunnel structures and possesses high practical value for engineering applications.