Abstract: Tri-axial compression tests are carried out on the layered sandstone specimens taken from the QEX Tunnel located in Xiangxi of Hunan. The results show that the strength of the rock is obviously anisotropic and there are two distinct failure modes， i.e.， one is the failure caused by sliding along the discontinuity and the other is non-sliding failure mode in which fracturing of rock material， fracturing across the discontinuity and the mixed mode of the above. Then a non-linear failure criterion for the layered sandstone is proposed to reflect different failure modes using different methods. Performance of the failure criterion is tested for validation against tri-axial compression tests data for the layered sandstone specimens. It shows that predicted values are in good agreement with experimental test data. The applicability of the failure criterion is also examined using the published experimental data of various types of layered rock mass.

Key words: layered rock mass, bedding structure, tri-axial compression test, failure mode, nonlinear strength criterion