A Research On The Seismic Response Of The Debris Landslide

The seismic response of the slope is a hot issue affer "5.12" earthquake , and it is also a multidisciplinary problems of engineering geology, seismology, geophysics . So the research level is still low in domestic and foreign, especially for the seismic response of the debris landslide.On the base of summarizing the types, topography, material structure, surface morphology and other characteristics of the debris landslide, the law of the seismic response about the effect of the basic geological conditions and the characteristics of seismic wave parameters (frequency, amplitude, propagation direction) was been got through collecting the typical dynamic response example in the"5.12", then the law is been carried out by numerical simulation. Last three typical dynamic response of debris landslide example ware studied in-depth, demonstrated the different resurrection control factors. The following rules and conclusions drawn:(1) In the case of the lower slope , eg less than 100m, the displacement ,velocity and acceleration were increasing with the slope height. The contour of the amplification coefficient was approximately equidistant distribution, but when the slope was high , eg, greater than 300m , the displacement velocity acceleration was no longer with the increasing of height by line. Formatting of a number of extreme value trap, so the maximum and minimum values were showed in the rhythm changing. Therefore, the"Vertical Zoom"of the slope was existed only with a certain height.(2) The infection of the slope gradient on the dynamic response is not linear, the acceleration amplification factor is not increased with the rising slope, and has a peak at about 40°, before the 40°the amplification factor rising with the gradient, after the 40°the amplification factor debasing with the gradient.And the gradient of the old landslide is not more than 25°, which indicate that the debris landslide responsing to the seismic wave is not sensitive.(3) The weak material within slope, such as the slip zone or the fracture zones is presented under the dual character on the stability of dynamic conditions. Because the two different elastic modulus of materials, the resulting reflected wave is tensile wave, which produces tensile stress at the interface, and the two E-value larger difference, the higher the tensile stress value. It is clearly unfavorable for the stability of the landslide. As the strain increase of the weak layers, its stiffness decrease, damping increase, the filtering effect of soil increased, large number of seismic wave energy is been absorbed. When the slip zone is dense and thickness, it can withstand the shock tensile residence and shear effect, then the slip zone plays a role as a barrier to stop slope about the seismic waves.(4) The requency, amplitude, propagation direction of the seismic wave have a closely related with the slope dynamic response. First of all, the others under the same conditions, the extreme egion of the acceleration amplification factor occurs more frequently under the high frequency wave effecting, and the amplification coefficient value lower than the low-frequency waves of amplification factor, which has relation with the absorpting the high-frequency wave effect of the rock and soil. Seismic wave amplitude is mainly to change the acceleration amplification factor within the slope. The two are proportional, but the amplitude amplification factor does not change the size of the shape contour. When the propagation direction of the landslide in the same direction, the body is not conducive to the slope stability, and when the two opposite directions, the power wave on the slope of the dynamic response is limited.(5) Under natural conditions before the earthquake, the stability of the landslide in earthquake timeing an after the earthquake has important implications on deformation and stability. When the stability of landslide that is low, even the site seismic intensity is low, the landslide alse may overall instability. Such as Shuiboxia 7# landslide, the intensity of the field area is onlyⅥin degree, but it resurrected generally in the "5.12" earthquake.(6) The overhead conditions of the landslide has important implications on the slope dynamic response. When the slope facing the space of two or three face empty, the "reciprocating effect" of seismic wave can easily destroy the original structure of the slope, increasing the disintegration of rock and soil. Such as Muliuping Landslide, its upstream region facing two empty, with the strong earthquakes, the landslide apparented displancement to the gully and slope ahead,the direction was not the same with the main slip direction. By contrast, the positive slip direction of Hejia Landslide was barriered by the tuff ridge in the upstream side of the border, the "reciprocating effect" of the seismic waves is limited. (7) As the landslide features, the deformation and failure of the landslide under the effect of the seismic waves is mainly as a "cumulative-type" damage, shows as the rock and soil relaxation, rupture, and forms tensile cracks, gradually forward "slip–rupture ", finally break, and rarely showed the overall moment of avalanche and high slip, as the overall revival of Shuiboxia 7 # Landslide and the local revival of Dujiangyan Maliuping Landslide is still slowly "creep", without an overall high-speed instability.