There are a large number of steep loess slopes in the northwestern region of China. The loess structure would be greatly reduced by rainfall or disturbance, which may lead to the occurrence of landslides. Therefore, it is of great theoretical significance to carry out the researches on torsional shear strength test and tensile strength test of structural loess. In this paper, firstly, the failure characteristics of structural loess are analyzed using a newly developed test device for torsion shear test. Secondly, based on the results of torsional shear test, the joint strength formula which can comprehensively consider the tensile and shear properties of structural loess is validated. Finally, an algorithm of calculating failure stress is derived based on the joint strength. The results show that the failure torques of intact loess and remolded loess gradually decrease with the increase of water content, and the failure torque of intact loess is greater than that of remolded loess. In the torsional shear test, the failure stress circle is tangent to the joint strength failure line, which verifies that the joint strength formula has a reasonable experimental basis. The joint strength and the derived algorithm of calculating failure stress can provide a more realistic way for the evaluation of loess slope disasters.

structural loess  /  tensile strength test  /  torsional shear strength test  /  triaxial strength test  /  joint strength