The Mechanism Research On The Fluidization Of The Landslide Translating Into Debris Flow

In this thesis, a general review is given on rainfall-induced flow slides occurring in tropical areas. A systematic study is conducted on engineering behaviors of residual soil, failure mechanism of residual soil slope and mechanism of natural flow slides triggered by rainstorm in Jiang Jia drainage area.To investigate engineering properties of disturbed soils, a series of tests, including grain-size analyses, permeability tests, direct shear tests and dynamic iriaxial lest is performed on specimens. The direct shear tests indicate that the strength of the soils is affected obviously by the quantity of the water in the specimens. The dynamic triaxial tests show that the strength reduces and the pore water pressure increase with the rising of vibration times. Based on the results of these tests, strength model and pore water pressure model have been advanced and validated. In addition, not only have the liquefaction mechanism of the soils been analysed, but also the influence of the factors on the extent of liquefaction of the saturated soils have been discussed.The fieldworks and the test results show that there appears three failure models on the natural slope, that is, rotational slide, translational slide and earth flows.Triaxal tests, including the isotropical consolidation drained and undrained compression and anistropically drained tests, are performed on loosely compacted specimens. The critical state line (CSL) is obtained in the e-lgp' plot based on the results of the above tests. The initial state of the consolidated specimens can be classified into dilative and contractive in the light of the soil state relative to the critical state line. The failure mechanisms of both dilative and contractive soils under the penetration of rainfall are analyzed. The soil is of perfect plastic behavior after peak strength in the stress-strain relationship in istropical consolidation undrained compression. The reason for the failure of loosely residual soil slopes triggered by rainfall is that the contractive failure caused by the penetration of rainfall, giving rise to a high excess pore pressure which reduces shear strength of the soil. The soil is prone to flow slide after failure under the action of gravity due to its high moisture content. The stress-strain behavior of the remolding sample indicated that the failure of residual soil slopes is not caused by static liquefaction.