The Centrifuge Model Test For The Sliding Mechanism Of High Fill Slope Pre-reinforced In Panzhihua Airport

With the large establishment of traffic infrastructures in western China, airport construction is in the stage of rapid development. These airports in mountain area generally posses the features of high fill, high earthquake intensity, and complex geological conditions. At present, there are more and more high fill slope failures, which cause severe and wide damages to life property and economic construction. Therefore, studies on sliding mechanism of high fill slope have certain directive meaning to engineering construction. Based on the No.12high fill slope of Panzhihua airport, the deformation-failure characters of pre-reinforcement high fill slope in natural condition and rainfall condition are stimulated in this paper by the500g·t large geotechnical centrifuge, thus reappearing the sliding mechanism of No.12landslide, and the sliding mechanism of No.12landslide is discussed in this paper. Main study achievements are described as follows:(1) Based on the No.12high fill slope of Panzhihua airport, the deformation-sliding process of the high fill slope, with length about300m and height about120m, is stimulated at the acceleration of245g by the500g·t large geotechnical centrifuge. The centrifuge model is made of the actual materials, three rows of anti-slide piles are stimulated in this model, and sixty testing elements are installed in this model, such as pore-water pressure gauge, earth pressure gauge, displacement sensor and strain gauge.(2) Laboratory soil tests, such as sieve test, particles gradation test, medium shear test of fill body and direct shear test of slip soil, show that values of c, φ with water content of fill body is12%are in accord with natural soil. Therefore, the actual fill soil is accurately stimulated, and the centrifuge model is in accord with the high fill body further.(3) In natural condition, as water gradually infiltrates, the pore-water pressure shows the trend of slowly increasing. Although there is no obvious sliding, subsidence and cracking appear in the top of model, minute uplift deformation appear in slope toe, and obvious shear strain zone appear in the trailing edge along the bedrock-cover interface. The phenomenon described above demonstrates that a shear creeping deformation appears along the bedrock-cover interface under gravity.(4) In rainfall condition, peak pore-water pressure appears at the acceleration of200g, and then pore-water pressure decreases rapidly due to the sliding failure; an obvious subsidence and large parallel tension cracks appear in the top of slope, and data of two monitoring points show that subsidence is about10cm; uplift appears in slope toe affected by the sliding deformation and squeeze of slope soil. In summary, tensile fracture mainly appears in middle part and after part of slope, and squeeze mainly appears in middle part and front part of slope, which shows the characters of plastic flow.(5) When acceleration keeps at245g, in natural condition, soil pressures of pile back along the depth are respectively210.6KPa at the middle of pile (40mm away from pile back),304KPa near the anchorage section (75mm away from pile back). In rainfall condition, soil pressures of pile back and pile front,40mm away from pile top, are respectively676KPa,452KPa. By comparative analysis of soil pressure in natural condition and rainfall condition, soil pressure of pile back are obviously larger than pile front, thus demonstrating pile back endures larger thrust force. According to the soil pressure analysis result of pile body, soil pressure of pile body is gradually increasing along the depth and maximum soil pressure appears near the bedrock-cover interface, therefore, the pile failure is caused by the shearing failure along the bedrock-cover interface.(6) By comparative analysis of centrifuge model and actual slope, deformation-failure characters showed by model are in accord with actual slope; the sliding mechanism is understood better by the aspects of deformation-failure characters, force situation of anti-slide pile, variation situation of pore-water and so on. The sliding mechanism is confirmed as creeping--progressive shearing--break sliding.