关键词: 堆积层滑坡, 离心模型试验, 降雨, 滑动失稳机制

Abstract: There was a heavy rain in Nanjiang County on September 16, 2011, causing a great number of debris landslides mainly sliding along the interface of soil and bedrocks. In order to study the formation mechanism of the shallow subsurface debris landslides induced by the heavy rainfall, a rainfall simulator is used to produce the rainfall during the test. The develop process of the landslide are simulated under rainfall by the centrifugal model tests and characteristic parameters of deformation and fracture are obtained. The analysis of the centrifugal model test results is performed to investigate the sliding mechanism of the landslide. The results indicate that: 1) The soil pressure and pore water pressure gradually increases with a greater acceleration, and the moisture content in the slope slowly reduces while the moisture content in the soil of slip zone increasing at 0 g ~ 50 g loading; 2) The soil pressure values from the earth pressure gauges SP1, SP2 continue to increase while the soil pressure values from SP3, SP4 slightly change, which indicates that the leading edge of the sliding body and the central body have been subjected to the thrust from the rear of the slide. 4 pore water pressure values gradually increase to the maximum and all of them reduce after the rain, which indicates that during the rainfall, pore water gradually converges to interface of soil and bedrocks , after the rain , pore water in the vicinity of interface of soil and bedrocks gradually dissipate. The value of moisture sensor MC3 in sliding body is observed to first become larger, and after 20 s, the value of moisture sensor MC2 imbedded in the slip zone soil also gradually increases during the rainfall. 3) 4 earth pressure gauges and 4 pore water pressure gauges are found to change a lot in value, and measured values of two moisture content sensors decrease rapidly, which suggests that the slope have a whole slide at this time. After that, earth pressure gauges SP1, SP2 and SP3 increase slowly to their maximum while SP4 has been declining; four pore water pressures gradually increases to the maximum, and after the second rain , four soil pressures, four pore water pressures and two moisture contents gradually reduce. 4) Finally, by comparing the model test with the prototype test, the sliding mechanism of the fill slope can be recognized as the slip-crack- whole sliding mode.

Key words: debris landslide, centrifugal model tests, rainfall, sliding mechanism