The 28 October 1996 landslide and analysis of the stability of the current Huashiban slope at the Liangjiaren Hydropower Station, Southwest China

On 28 October 1996, a landslide occurred on the Huashiban slope near the Liangjiaren Hydropower Station. The landslide was caused by a failure mechanism induced by an earthquake (Mw 7.0) at Lijiang on 3 February 1996, after which a tensile fracture zone formed on the Huashiban slope. The subsequent impact of several small earthquakes on the slope increased the tension crack connectivity and the tensile strength gradually decreased. Severe rainfall in the rainy season between May and October, especially in July and August, decreased the shear strength of the bottom sliding surface, resulting in a landslide on the Huashiban slope on 28 October 1996. The stability of the Huashiban slope is important for plant site selection. If a further landslide occurs on the slope, the Liangjiaren Hydropower Station project will be critically affected, so analysis of the current slope stability is extremely important. At present, the Huashiban slope can be divided into five subzones: (1) a landslide deposit zone; (2) a landslide zone; (3) a tensile fracture zone; (4) a crescent-shaped zone; and (5) an upper slide zone. Using historic landslide data for 28 October 1996, retrospective analysis of the landslide process revealed shear strength parameters for the Huashiban slope. The cohesion strength is 0.024 MPa, the friction angle at the bottom sliding surface is 14°, and the tension crack connectivity is 50%. These parameters were used to compute the stability of the Huashiban slope. Under the same conditions, the stability of the whole slope is better than that of part of the slope, and the overall stability is dominated by the tensile fracture zone. Under earthquake and rainfall conditions, it is possible that failure will occur in the tensile fracture zone. Thus, the Huashiban slope should be reinforced for construction and operation of the Liangjiaren Hydropower Station.