EXPERIMENTAL STUDY ON THE LATERAL FLOW SLIDE MECHANISM OF SATURATED LOESS MASS

In 1920, the Haiyuan Ms 8.5 strong earthquake induced many loess liquefaction landslides, which were characterized by low angle, long distance, fluidization, and even phenomenon of large-scale horizontal lateral spreading flow slide happened, and the special formation mechanism is quite controversial. The Shibeiyuan landslide was one of the most typical examples of these landslides. Based on the detailed exploration of Shibeiyuan landslide remains, with the application of the DPRI-5 ring shear apparatus, the stability deformation characteristics of the liquefied saturation loess was studied and the influence laws of factors like consolidation pressure, saturability and shearing speed on the steady state strength of loess was discussed. The research indicates that the dynamic load level and its action mode affect considerably the stress-strain of loess and the developing law of pore water pressure; at the same void ratio, the steady state strength of saturated loess is not affected by early stress path, but related to consolidation pressure, saturation, loading rate and so on. The main conclusions are as follows:1Under the undrained shear condition, the higher the consolidation pressure gets, the slower the pore pressure response, and the higher the steady state strength gets2 The higher the saturation of loess gets, the faster the pore pressure response and the lower the steady state strength gets. 3 Shearing rate has a certain weakening effect on loess strength. When the shearing rate is within the scale of 0.1 mm/s, it poses little effect on the steady state strength; when the shearing rate ranges from 0.1 to 1 mm/s, the steady state strength reduces to various degree as the shearing rate increases; when the shearing rate is more than 1mm/s, the steady state strength tends to be constant because the increase of shearing rate would reduce the effects. In general, the higher the saturation degree is, the greater of the weakening effect of the shearing rate poses on the steady state strength. It reveals that steady deformation characteristics and the disaster-inducing mechanism of horizontal lateral flow slide of the Shibeiyuan saturated loess layer under low steady state strength.