Abstract: Post-harvest Straw(termed PHS hereafter) and loess are easily accessible in Chinese Loess Plateau. The loess-PHS mixture has been widely applied to the construction of residential houses that have been utilised over decades under freeze-thaw cycles. Notwithstanding that, the shearing behavior of such a mixture has rarely been discussed by published literatures. Thus,a consensus about its shearing behavior has not been reached yet. In this study,the shearing behavior of loess-PHS mixture is investigated using a series of large-scale direct shear(LSDS) tests and the mechanism of improving the shear strength parameters of loess-PHS mixture is analyzed as well. The PHS is firstly treated with hot water and then blended with loess for preparing cubic specimens with moisture content of 14%,18%,and 22%,respectively. The LSDS test results demonstrate that:(1) the PHS added into specimen impedes particle rearrangement and results in particle inter-locking,thereby restraining the development of shear bands in the adjacent of shear plane and leading to an improvement of friction angle;(2) the optimal dosage of PHS is deemed as 0.55%-0.65% considering specimen homogenisation and testing reliability;(3) the vertical displacement observed before and after the shear box can be used to explain the gradual increase of the strain-hardening curve(continuous development) and the strain-hardening curve(two stages of continuous development).

Key words: reinforced loess, post-harvest straw, direct shear test, shear strength, optimal dosage, Chinese Loess Plateau