As waste landfills continue to expand, accidents can occur if these landfills are not properly stabilized. In this study, samples of municipal solid waste (MSW) from a waste landfill in Xi'an, China were collected through on-site drilling. Considering the effects of eight landfill ages (1, 2, 3, 11, 12, 13, 21, 22, and 23 y) and six moisture contents (natural, 20, 40, 60, 80, and 100%), 324 groups of MSW were tested in the laboratory with a direct shear test apparatus. The results indicate the following: (1) with an increase in horizontal shear displacement, the shear stress of MSW gradually increases without a peak stress phenomenon, which is a displacement hardening curve; (2) with an increase in landfill age, the shear strength of MSW increases; (3) with an increase in moisture content, the shear strength of low-age MSW first increases and then decreases, but the relationship between shear strength and moisture content of medium- and high-age MSW is not significant; (4) with an increase in landfill age, the cohesion (c) decreases, and the internal friction angle (φ) increases; (5) with an increase in moisture content, the c and φ of low-age MSW first increases and then decreases. Based on these results, a shear strength, landfill age, and moisture content correlation model is established, and the model has a high degree of fit with the overall experimental data. The results of this study can provide a reference for the stability calculations of MSW landfills.
