Landslide experiments on artificial and natural slopes

Abstract

An almost real-size slope model was used to study the initiation process of landslide fluidization during torrential rain. Experiments were conducted by filling an inclined flume with loose sand under the rainfall simulator to induce the sand to collapse. Both the movement, volumetric strain and the pore water pressure of the sand were monitored throughout the experiments, from the start of spraying to the cessation of the landslide. These experiments showed: (1) Landslide fluidization caused by undrained rapid loading undergoes three stages: compaction of the sand layer by the sliding mass from upper slope, generation of excess pore water pressure in saturated zone, and induction of fast shearing; (2) Fluidization at the collapse source area undergoes also three stages: destruction and compaction of sand layer skeleton by outbreak of shearing, increase of pore water pressure in saturated zone, and shift to hispeed shearing, these three stages take place almost simultaneously. An experiment to induce a fluidized landslide by artificial rainfall was conducted on a natural slope at Mt. Kaba-san in Yamato village, Ibaraki Prefecture, Japan. The experimental slope was 30 m long, 5 m wide, and the average slope gradient was 33 degrees. A landslide initiated 24627.5 s (410 min 27.5 s) after the start of sprinkling at a rainfall intensity of 78 mmhr-1. The landslide mass was 14 m long and 1.2 m deep (at maximum). It first slid, then fluidized, and changed into a debris flow. The travel distance was up to 50 m in 17 seconds. The apparent friction angle of the fluidized landslide was 16.7 degrees. Formation of the sliding surface was detected by soil-strain probes. Motion of the surface of the failed landslide mass was determined by stereo photogrammetry. © 2007 Springer-Verlag Berlin Heidelberg.