Abstract: The use of rubber particles and soil mixture for foundation backfill poses a technical challenge in terms of engineering performance, including increased settlement and insufficient bearing capacity. This paper proposes the use of cement slurry to address these limitations. The resonant column test method was used to analyze the influence of changes in peripheral pressure and the rubber and cement content on the dynamic characteristics of the composite soil body. The results show that the rubber and cement content and effective circumferential pressure are the main factors affecting the decay of the normalized shear modulus ratio G/G_max and the growth of damping ratio λ of the mix. An increase in the rubber content increased the modulus reduction curve, slowing the attenuation rate of the modulus ratio while simultaneously increasing the damping ratio curve. A higher confining pressure suppressed particle displacement, reduced the modulus ratio decay rate, and lifted the modulus ratio curve; however, the damping ratio was decreased. An elevated cement content enhanced interparticle bonding, increased the modulus ratio curve, and reduced the attenuation rate while lowering the damping ratio curve. Based on the variation pattern of the maximum dynamic shear modulus G_max with rubber content at a fixed cement content of 3.5 g/100 ml, a predictive formula for G_max of the cement rubber sand mixtures was derived. Recommendations regarding the parameter values for different working conditions are also provided.