Abstract: The experimental research on shear properties of geocell reinforced soil and geocell reinforced cement stabilized soil was carried out by using a large size direct shear equipment (500 mm?500 mm?400 mm, length?width?height) which was developed by South China University of Technology. Through the experiments, the shearing process of geocell reinforced soil was simulated. The shear strength indices and its strengthening theory by mechanics were determined. The experimental results show that the relationship curve of shear stress to shear strain of geocell reinforced soil is nonlinear. In addition, the cohesive force index was increased greatly. The friction angle was increased relatively less. Furthermore, on the purpose of understanding the influences of testing methods, three kinds of shear tests including regular direct shear test, large size direct shear test and triaxial compression test with in-situ soil and 5 % dosage of cement stabilized soil were conducted. The corresponding shear strength indices of different kinds of testing methods are in sequence from less to more as below: Friction angle of soil: triaxial compression test less than large size direct shear test less than regular direct shear test. Cohesive of soil: large size direct shear test is less than triaxial compression test less than regular direct shear test. Friction angle of cement stabilized soil: triaxial compression test is less than large size direct shear test. Cohesive force of cement stabilized soil: triaxial compression test less than large size direct shear test.

Key words: geocell, large size, direct shear test, triaxial compression test, cement stabilized soil