Study On Dynamic Load Laws And Attenuation Laws Of Parameters Induced By Rainfall Of Colluvial Landslide And Its Stability Evolutional Laws

Supported by the National Natural Science Foundation, selecting the landslideinduced by rainfall as the research object, according to the saturated-unsaturatedseepage theory, hydrodynamics theory and indirect coupling analysis theory, using thefinite element software GeoStudio adequately, the space-time laws of dynamic load andattenuation of strength parameters of colluvial landslides under rainfall are analyzed andconcluded. Parameters of transient saturated zone and unsaturated zone step in everyarea and every step are assigned by using the indirect coupling method and finiteelement software GeoStudio to conclude the evolutional laws of displacement field andstability of landslides when concerning the coupled catastrophic effect of load andattenuation of strength parameters. The comprehensive prevention measures of drains,draining well and concrete surface protection are put forward combined with the aboveresearch results. Based on the above research, the following conclusions are drawn:1. Rainfall infiltration is the process of load for slope including the weighting andattenuation of matrix suction. The top, leading edge and high position of the slope firstload and the increased loads are larger under rainfall, and areas and magnitude of loadexpand and increase constantly along with the increase of intensity and duration ofrainfall.2. When the moisture content increases, the cohesive force presents obviousnonlinear attenuation rules while the internal friction angle presents approximatelylinear attenuation rules, these rules are especially obvious for colluvial soils. Theattenuation degree of C is obviously bigger than that of φ, and the attenuation degrees ofstrength parameters of colluvial soils are between cohesive soils and rock soils.3. Under the same duration and intensity of rainfall, the displacement in centralzone is greater than that in leading edge, the displacement in leading edge is greaterthan that in trailing edge. The displacement in surface layer is greater than that in deeppart. The magnitude of displacement in each part increases constantly along with theincrease of intensity and duration of rainfall. 4. As rainfall goes on, the depth of the potential sliding surface of slope changesfrom deep to shallow gradually, the shear surfaces in leading edge upraises gradually.5. The load effect runs through the entire rainfall process, until the increase ofslope body moisture content with the rainfall going on at the late time, does weakeningeffect appear, following which the slope stability reduces quickly. The attenuation rateof stability coefficient induced by coupled catastrophic effect is larger than that inducedby weakening catastrophic effect, the attenuation rate of stability coefficient induced byweakening catastrophic effect is larger than that induced by load catastrophic effect. Thelonger the rainfall duration, the more obvious attenuation of slope stability coefficient,and the more obvious differences among the attenuation rates of stability coefficientinduced by three kinds of catastrophic effects.6. Combined with the previous research results, comprehensive preventionmeasures of setting opening drains in trailing edge, draining well in middle part andconcrete surface protection in leading edge are put forward. Analysis results show thatthe prevention effect of comprehensive measures is well.