Due to the existence of fibrous materials such as plastic fragments, the strength anisotropy of Municipal Solid Waste

(MSW) materials is the main source of differences between their mechanical response in direct shear and triaxial apparatus.

As an extension of earlier research on the mechanical behavior of MSW using a large traixail apparatus, results presented in

Shariatmadari et al. [1] and Karimpour-Fard et al. [2], the current study was programmed and executed. MSW samples were

tested using a computer controlled large shear box apparatus with normal stress levels ranging between 20 to 200 kPa. The

effect of fiber content, fiber orientation, aging and shearing rate on the response of MSW were addressed. The results showed

that shear strength of MSW increases with normal stress, although, in spite of the presence of reinforcement elements in MSW

and unlike the results from triaxial tests, no strain hardening could be observed in their mechanical response. An increase in

the shear strength of MSW was observed with increasing the shearing rate. Increasing the shearing rate from 0.8 to 19

mm/min, enhanced the shear strength of samples from 16 to 27% depending on the shear displacement level. Although, the

same trend was investigated in traixial tests, but lower rate-sensitivity in the mechanical response of MSW in direct shear tests

were observed.

Unlike the results of triaxial tests with aging process, mobilized shear strength level of MSW samples tested under direct

shearing decreased comparing fresh samples. It was also observed that altering the fiber content and their orientation could

affect the mechanical response and shear strength of the MSW. Additionally, there is an optimum fiber angle in MSW which

yields the highest level of shearing strength.