Stress-Controlled Direct Shear Tests of Shearing Behaviour of Lantian Loess Reinforced with Straw Fibers

The loess tends to behave in an instable manner when subjected to external loads since it is characterized by metastable structure, high porosity, and water sensitivity. Therefore, the Chinese Loess Plateau has considered as a landslide-prone area in northwest China. This study explores the potential of using the loess-straw mixture as an alternative backfill material to improve the stability of loess against shallow slope failure and functionalize the agricultural solid waste. The displacement-controlled direct shear tests aim to document the baseline shear strength parameters of the loess specimen with and without straw waste inclusion, whereas the stress-controlled direct shear tests reveal the temporal relations of horizontal and vertical displacement under given shear stresses. The mechanism of causing the increase in shear strength is revealed. Furthermore, the stress state at failure in a displacement-controlled direct shear test and a stress-controlled direct shear test for same specimen under equal testing conditions show good correspondence to each other irrespective of testing method, and their results approximate a single failure envelope.